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Astrophotography - Tips and tricks please.

theandies
Enthusiast

So I finally got a good consumer DLSR, the T6i.  My T mount adaptor comes in friday.  I didn't get a shutter release yet but with the T6i I think the remote control through my cell phone will keep the vibrations down.......I guess.  I've always wanted to get into astrophotography but never had a camera that could do it.  I've read quite a bit about it over the years but I'll be new to it just as I'm new to anything other than a point and shoot and cell phone cameras.

 

 I have an old school (no electronics but I know how to use it very well) Meade 8" Schmidt–Cassegrain that I've had for years.  I do have an off axis corrector and a very good tripod.   I'm just looking for some hints and tips from the astrophotography buffs here if there are any.  What I think I'll try first is planetary pictures and pictures of the moon. After I get the hang of the basics I'll get more ambitious.  Anything would be much appreciated. 

 

Thanks

John

2 ACCEPTED SOLUTIONS

TCampbell
Elite
Elite

Most LX200 scopes are f/10, but there were some f/6.3 models and the new LX600 and LX850 models are f/8.  You'll want to know what focal ratio you have because when you use a camera with a telescope there's no adjustable f-stops like there is for a lens.  You'll be doing manual exposures and you'll want to know what your native focal ratio is.

 

When you connect the camera, connect it "straight through" (no 90º diagonal).   I have a 14" LX200 ACF -- which has longer forks and I have a LOT of clearance behind the optical tube.  My scope can point straight up through the fork arms with an electric focus and my Canon 60Da attached and still have plenty of room so that there's no danger of the camera hitting the base if the optical tube tries to point straight up.  

 

Check the clearance on your scope (with camera attached) to make sure you are comfortable knowing that you have enough clearance -- as this will avoid potential damage if you slew to a new target in the dark and the camera crashes into the base.

 

My LX200 has an electric focus with visual back (standard 2" tube opening for a 2" eyepiece or 2" diagonal) and so my camera uses a 2" diameter nosepiece with the EOS t-ring.  I don't use the SCT T-mount.  

 

When focusing the scope, always "finish" turning the focuser into focus in the counter-clockwise direction.  The LX200 has mirror-shift when you reverse the direction of focus.  This is because the focus knob either pushes or pulls on the primary mirror at the back of the scope and the mirror rides on a central baffle that has to allow at least a tiny bit of slop so that it can slide easily.  When you "push" the mirror forward, it gets the best support from the bottom and also forces the mirror to rest in a properly collimaged position.  When you "pull" the mirror back, it slightly de-collimates your optics and ALSO the mirror may eventually settle on you in mid-exposure (that would ruin the image being captured at the time).   By finishing focus while rotating the knob in the counter-clockwise direction, you give the primary mirror the best support, collimation, and it reduces the potential for the mirror to settle and move after you finish the focus.

 

The LX200 has a mirror-lock knob and when I do visual astronomy I don't use it.  But when I do imaging, I DO use it.  My scope has an electric focuser on the visual back.  That means I can adjust the main focus, lock the mirror, then use the electric focuser to fine-focus the telescope to my satisfaction.  

 

I prefer to point the scope to a pinpoint star to focus.  Focusing on the moon or a planet is is not quite as easy to see if you achieved perfect focus.  But when you've minimized the size of a pinpoint star, you'll have more accurate focus.  

 

There is an application called "Backyard EOS" which is built for astronomy astro-imaging using Canon EOS cameras.  It has focus aids as well as both planetary imaging modes and deep-sky imaging modes.  It controls the camera and performs image acquisition for you (it's basically "tethered" remote shooting control of the camera.)

 

I normally use a Bahtinov focusing mask on my scope to achieve fine focus for deep-sky images.  But a lot of imagers I know have electric focusers and use a program called FocusMax which is exceptionally accurate focus.  FocusMax deliberately de-focuses a star (you see the donut shape) and starts focusing and imaging and focusing and imaging.  It measure the size of the donut and does several runs creating plots.  It mathematicaly determines where the perfect focus point must be located (even if sky conditions are horrible.)

 

Both "Backyard EOS" and "FocusMax" require Windows (I use a Mac so I don't use them, but they are popular.)

 

The moon is a VERY easy target... the correct exposure for the moon follows the "Loony 11 Rule".  That rule says that at f/11 (and it only works at f/11) you can set the shutter speed to the inverse of the ISO sensitivity.  So at f/11 and ISO 100, it'd be 1/100th sec.  At ISO 400 it would be a 1/400th sec exposure, etc.  

 

If your scope is really an f/10, it's close enough... f/10 is approximately 1/3rd stop more light than f/11 (it's not a significant difference) but it means the moon will be slightly bright.  You can adjust the shutter speed 1/3rd stop faster to compensate.  E.g. instead of 1/100th sec you should shoot at 1/125th sec. and be bang-on the accurate exposure again.  If you have an f/6.3 scope then you are 1.6 stops faster (almost, but not quite 2 stops).  That means insead of ISO 100 and 1/100th, you'd want to shoot at ISO 100 and 1/320 sec.

 

Planets are slightly more difficult... they are dimmer than the moon so you'll use a higher ISO setting.  But they are typically imaged by shooting about a minute's worth of video frames.  Stacking software is then used to identify the best frames out of the video and those are combined to create a composite image.

 

If you happen to image Jupiter, note than Jupiter has a fairly fast rotational speed... the surface changes enough in MERELY 10 minutes that if you try to combine images shot more than 10 minutes apart you'll get blur.  All the data you capture for Jupiter needs to be captured within that 10 minute window of time.  There is a program called Registax that is particular popular (and free) for planetary image stacking.  

 

If you image Saturn, it's low in the sky this year (because it's an "outer" planet and our northern polar axis is pointed toward the sun.  That puts saturn low relative to the horizon for astronomers who live in northern latitudes.)  This means you'll get some atmosphereic dispersion when you view it.  Atmospheric dispersion is a form of chromatic aberration -- except it's caused by our atmosphere working like a lens.  The atmosphere splits "white" light into the rainbow spectra of light.  You'll see a "red fringe" on one edge of the planet and it's rings... and a "blue fringe" on the opposite edge.  Not to worry... one of the features of Registax is that it can separate the single color image into red, green, and blue color channels and it lets you "shift" them back on top of each other.  This greatly improves the focus quality of your image.

 

Deep sky objects are particularly difficult.  This may cause you to lose all your hair.  You have been warned.  🙂

 

To detail how to take deep-sky images would take a while... but I can sum up:

 

The scope needs to be mounted on a "wedge" (e.g. such as a Meade Superwedge).  The wedge is moutned to the tripod and the scope is then mounted to the wedge.  The wedge is tilted so that the tilt angle is adjusted for YOUR viewing latitude.  If the scope is merely on an alt-az mount then you'd get field rotation as you imagine and that would create blurred results.

 

You mentioned your scope does not have "electronics" but it would need to minimally have an RA drive that can track at sidereal speed.  Do you have this?

 

The mount needs a "precise polar alignment" (which takes a bit of effort.)  

 

You take numerous long exposure images (e.g. 5-10 minutes would be typical).  

 

You also need to capture "dark" frames, and it's also helpful to grab "flat" frames and "bias" frames.  I can explain what these are if you haven't heard of them.

 

The images are then stacked using image registration and integration stoftware (for deep sky objects there's a free program called "Deep Sky Stacker".  I use something called PixInsight do do my registration & integration (stacking) but PixInsight isn't free.

 

You mention this is an "old school" LX-200 with "no electronics".  Are the electronics fried?  I've seen a number of LX200 models and some have very old primitive electronics, but I've never seen one that doesn't have any electronics.    There are places that will either repair or refit the scope so that it does have working electronics.  Finding the very old original boards in working order is tough.  There were some bad capacitors used which would dry out over time and then blow.  The guys that service the scopes know which ones blow and they replace them with modern equivalent capacitors that wont blow BUT it's critical that they do it BEFORE the scope has a problem.  If the capacitors blow before being replaced they often take out other electornics on the board and now it's a more serious repair.  Those "more serious" repairs can involve trying to find replacement boards that aren't made anymore, haven't been made in years, and are becoming increasingly rare.

 

So... now there are services that simply pull the original boards and replace them with completely new boards, but the refit kits give you electronics that work like an LX90 (not an LX200).  LX90's dont' have PEC -- so they aren't as precise as LX200's, but it's still better than nothing.

 

Moon shots are easy (no elecronics needed.)

Planetary shots are fairly easy but it helps to at least have a working RA drive that can track at sidereal speed (clock-drive) even if there are no computerized go-to electronics.

 

Deep-sky objects, however... will really need working electronics and an autoguider.  This are the most complicated images by far --- because they require such long exposure times.  And during those very long exposures, you can tolerate any movement or tracking errors -- otherwise it ruins the image.

 

Tim Campbell
5D III, 5D IV, 60Da

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Yes, check out Fred Espenak's page (aka "Mr. Eclipse").  Fred is a retired NASA physcicist who does all their eclipse predictions and a top expert on eclipse photography.

 

http://www.mreclipse.com/SEphoto/SEphoto.html

 

Assuming you will be in the path of totality...

 

Also, it's best to have the camera under computer control so that you can enjoy the eclipse instead of having to pay attention to your camera.

 

If you have a Mac, then you may want to download "Solar Eclipse Maestro".

If you have Windows, then you may want to download "Eclipse Orchestrator" or "SETnC".

 

I'm familiar with Eclipse Orchestrator and Solar Ecipse Maestro, but not SETnC.

 

Solar Eclipse Maestro and Eclipse Orchestrator both allow you to script the eclipse capture but the timings are based on the eclipse path prediction data and your precise location (either via GPS or manually entered). 

 

The shots before and after totality are shot with the solar filter on.  

 

Double check frame & focus a minute or two before totality (with filter still on camera).

 

At 20 seconds prior to totality (and no sooner than 50 seconds prior to totality) you can remove the filter but DO NOT LOOK THROUGH THE CAMERA once the filter is off (that's why I mentioned doing the final frame & focus before removing the filter).

 

At about 9 seconds prior to totality you may see the "Diamond Ring" effect.

At about 1.5 seconds before you may see the "Baily's Beads" effect.

 

The software script can be set to announce warnings (e.g. 5 minutes to totality, 2 minutes to totality, when to remove filters, etc.) so you know when to do each step.

 

Once totality begins, it is safe to look directly at the sun.  You'll see the solar corona.  It has tremendous dynamic range and requires about 10-12 stops of bracketed exposures to capture the entire corona (you can merge the shots with HDR processing).

 

Once totality ends you'll likely get another Baily's Beads, followed by another Diamond Ring.  After you capture that, it's time to put the filters back on the camera (which should happen about 20 seconds after totality ends.)

 

 

Solar Eclipse Maestro is free for non-commercial use (he charges if it's meant for commercial use).  He does appreciate donations.

 

Eclpse Orchestrator has a free mode which limits it's functionality, but it's a paid license to unlock all features.

 

Both Eclipse Orchestrator and Solar Eclipse Maestro use the same scripting language.

 

I have not used SETnC.  What I've learned about it is that it (a) runs on Windows, (b) only controls Canon cameras (no support for any other brand), and (c) it's free.

 

 

Clear skies & good luck!

 

Tim Campbell
5D III, 5D IV, 60Da

View solution in original post

40 REPLIES 40

It's tough when the sky doesn't cooperate with steady seeing.

You can buy a 15' tethering cable. Mine was less than $10 (there are vendors who charge $30-40 for one.) Search for a 15' USB type A male to mini-b and you should find several options.

Have fun!
Tim Campbell
5D III, 5D IV, 60Da

theandies
Enthusiast

Yes but it was my fault mainly as I was trying to observe right after sunset so the atmosphere was really turbulent because of the daytime heat still rising.  I have the next couple of days off and I'm on vacation starting next Wednesday so I can stay up late to let the atmosphere settle down. 

 

Also, I let my kids use my scope a while back (they set it up and put it away, I was not there) and I think they may have done something to the focuser.  I have a lot more mirror shift that I used to have and very little movement of the focus knob to fine tune the object before going out of focus completely.  Not to mention the old girl is almost 20 years old.  I think I'll have to send it in and have it looked at unless I can find some instruction on how to take it apart if it doesn't need any special tools or alignment fixtures to keep the mirror straight. I'm an engineer that works on robots so I'm pretty good with tools and such. I've also built a few telescopes in the past.  This was the first commercial scope I've ever bought.  I've searched for a service manual for it but so far cannot find it on the net.

I just did a Google search for "Meade 2080 manual" and this hit pops up:

 

http://www.cise.ufl.edu/~jnw/meade2080-2120manual.pdf

 

It does appear to be the full manaul.  I couldn't find the manual at the Meade website.

 

As for the mirror shift... from time to time, owners suggest running the focuser all the forward (turn it counter-clockwise until you feel it stop), then run the focuser all the way backward (clockwise until it stops).  That helps re-spread the lubricant. 

 

Also, you'll noitce more image shift using a higher power (low focal length) eyepiece than you will using a low-power (high focal length eyepiece) -- just because of the increased magnification.

 

If you have scope questions, you might want to join the users group at the Yahoo Groups website:

 

https://groups.yahoo.com/neo/groups/Meade_2080/info

 

I'm in the Yahoo Group for several telescopes I either currently own or previously owned (LX200GPS, Meade ETX Owners, ETX-LS, and LuntSolar groups and find them to be great resources when I run into issues or have specific questions.)

 

Tim Campbell
5D III, 5D IV, 60Da

theandies
Enthusiast

I have that manual somwhere at home and also have downloaded it but thanks for the link.  I was looking more for an actual maintenance manual not a user manual.  I did find some stuff on taking apart a Celestron  CAT and the guy who made that writeup said Meades were simular. 

I'll try the your suggested trick.  I can't remember which eye piece I was using at the time.  I think it was my 20mm so it wasn't that high.  I'll be sure to checkout the user groups you mentioned as well. 

Hopefully I'll have a clear sky tonight to see Venus and Jupiter together!!!!

theandies
Enthusiast

So I've finally found some time to take some pictures.  I was out of town for almost a month for work so that got in my way.

I did manage to fix my focus shift problem (before going out of town) that my 2080 was having by taking it apart and finding the grease was all dried out. I did a collimation check with a bright light after reassembling the scope but forgot to fine tune it the other night on a star (forgot) before taking the pictures.  This might explain the slight out of focus look.

I used Cannon Connect on my phone to work the shutter.  That worked out pretty good.  I took this shot right after sunset that is why the background it so blue.  I kind of like it other than it's a bit overexposed (to me anyway)

Here is the picture (.jpg I do have a RAW version)

20150822200833_IMG_0681.JPG

 

Image data:

681 data.JPG

Of course this was in Auto mode with the flash turned off.  I tried to take a pictue of Saturn but could not get the focus right before it dropped behind the trees then I realized I hadn't performed a fine tune collimation adjustment.  While doing that Murphy's Law cropped up and my cameras battery died. 

 

I am going to try again tonight.  Any suggestions on manual settings are greatly apprciated.  It should be a good night of seeing as a cold front came through yesterday and it should be good seeing conditions tonight.

 

Nice to see you have things working!

 

As you noticed, it's over-exposed.  But it's easy to get a correct exposure when imaging the moon because it's brightness is consistent (since the Sun is illuminating with a consistent amount of light).  You can use a guideline called the "Loony 11" rule. "Loony" for the moon (a bad play on "Lunar") and "11" because the relationship explained by the rule only works at f/11.

 

That rule says:  If you use f/11, you can set the shutter speed to the inverse of the ISO setting.  

 

Based on this rule, a photographer could use f/11, ISO 100, and 1/100th.  Or ISO 200 and 1/200th, or ISO 400 and 1/400th, etc.

 

But you don't have an f/11 scope... it's an f/10 scope (and telescopes don't have adjustable aperture blades or waterhouse stops) -- so you are 1/3rd stop faster than f/11.  But that means you can just dial the shutter to 1/3rd stop shorter duration of the ISO (that's one click on your shutter speed dial) and you're back in business.

 

So... whereas you could use f/11, ISO 100, and 1/100th sec... you are at f/10, but you could use ISO 100 and 1/125th sec exposure time -- and this would nail the moon for you ... every time!

 

The exposure below was taken using the "Loony 11" rule.

 

Moon

 

The surface of the moon has an "albedo" of .12 -- the "albedo" is the surface reflectivity or you can think of it as the amount of light that is reflected back off the surface expressed as a fraction of the total light.  So .12 means 12% of the light that hits the surface will be reflected back.  This happens to almost exactly match the surface albedo of a "worn aspalt" road (not freshly laid aspalt -- which is darker.)

 

Saturn will be more difficult and capturing Saturn will be easier if you put the camera in "video" mode, reduce the resolution to 640x480, and capture about 30 seconds to perhaps 1 minutes worth of video.  You can then use "Registax" or "AutoStakkert" (both are free programs) to perform image stacking and this will result in a much cleaner image after processing. 

 

There are numerous videos on how to use either program to do planetary imaging.

 

One more thing...  Saturn is very low in the sky (Earth northern axis is pointed toward the sun in summer, but that means our northern axis is pointed away from Saturn.  This puts Saturn low in the sky for northern hemisphere observers at that time of year.)  As a consequence, the atmosphere will distort your view of saturn by acting like a lens or prism.  It will disperse the light  so that the light is starting to split into a rainbow spectrum.  If you look closely at saturn, you'll notice one edge of the planet has a blue fringe on the edge... the opposite side has a red fringe.  This will result in a blurring of the entire object (even if the scope is in perfect focus).  The image processing programs (I know Registax has this feature and I think (but am less certain) that AutoStakkert can do it too)) have the ability to split the image into it's red, green, and blue channels, and then slide them back together again so they converge into a sharper image.  (In the old days when astrophotography was done with film there used to be a prism type device called an "Atmospheric Dispersion Corrector" or "ADC".  You can still buy such a device and a "cheap" one would be about $500.  But thanks to digital imaging technology and image processing software, you can digitally correct for this and do not need to buy an ADC.

 

Tim Campbell
5D III, 5D IV, 60Da

Thanks again Tim.  Of course the past few days have been clear up until sunset so I haven't been able to get out again.......go figure.

I'm not sure where you live but.... on September 27th (a Sunday) there will be a full lunar eclipse. I'm in the US Eastern time zone and for us the eclipse begins shortly after sunset/moonrise (a full lunar eclipse can only happen at the full moon and on that night the Sunset and Moonrise are pretty much teh same time with the Sun setting in the west as the Moon is rising in the east.

The farther west you are, the more the eclipse will already be happening by the time you see the moonrise (it's ideal to be in the US Eastern time zone).

But... if you live in the right area, that would be a GREAT time to go photograph the moon.
Tim Campbell
5D III, 5D IV, 60Da

I live in Virginia and have been looking forward to that event for a while.  Can't wait as I might even be on the coast that weekend!  My parents and brother live on the coast of NC about a block from the beach. 


@TCampbell wrote:
I'm not sure where you live but.... on September 27th (a Sunday) there will be a full lunar eclipse. I'm in the US Eastern time zone and for us the eclipse begins shortly after sunset/moonrise (a full lunar eclipse can only happen at the full moon and on that night the Sunset and Moonrise are pretty much teh same time with the Sun setting in the west as the Moon is rising in the east.

The farther west you are, the more the eclipse will already be happening by the time you see the moonrise (it's ideal to be in the US Eastern time zone).

But... if you live in the right area, that would be a GREAT time to go photograph the moon.

Thanks for the "heads up", Tim. We too are in the Eastern time zone, not too far from its eastern edge, So I'll definitely watch for it. The only problem is the tradition of clouds for eclipses in New England. I can still remember chasing around central Maine trying (unsuccessfully) to get out from under the clouds at the July 1963 total solar eclipse.

Bob
Philadelphia, Pennsylvania USA
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