03-13-2019 05:24 PM
I recently attended a training program at an observatory and the conversation eventually got around to our choices of cameras.
if you are an avid astrophotographer, I’d be interested to hear from you.
1. What DSLR camera do you utilize? Make and model, please.
2. Has it been modified at all to eliminate IR filters? If so, where, and/or by whom?
3. Do you load your photos to a laptop from a telescope, or do you take photos with your DSLR camera through the telescope?
4. Assuming you utilize a Canon camera, what lenses do you use? What prime lenses? What telephoto? What wide-angle or telephoto zoom lenses?
5. What photo processing software do you use, such as RegiStax or StarTools? Post processing software, such as Lightroom. Adobe, or DPPS?
Would love hearing from you.
04-13-2019 01:41 PM
I use a Canon 60Da, a ZWO ASI128MC-Pro, and a ZWO ASI174MM-Cool for my cameras (I also have an ASI174MM-Mini that I use as a guide-camera).
The Canon is a special edition of the 60Da that is pre-modded by Canon for astrophotography. A normal camera cuts the reds quite a bit becuase human vision isn't particular sensitive to reds (there's a lot more red in the world than we actually see). The key band is the Hydrogen alpha wavelength. Around 90% of all ordinary matter in the universe is hydrogen. This means loads emission nebulae glow in Ha. Traditional camera is blocking around 75-80% of the light at that wavelength. A modded camera tries to allow nearly all of it to pass. If you're imaging Ha objects (horsehead nebula, rosette nebula, lagoon nebula, etc. or even wide-field stuff like Barnard's loop) you would have to collect a lot more data to get the reds to show up vs. the modded astrophotogrpahy camera.
The ASI128 is a full-frame color camera with a cooling system that can chill the image sensor down to 40°C below ambient temp to reduce thermal noise. The "pro" in the name means it has an internal DDR buffer so that it can "read out" the sensor much faster (even if the computer can't keep up) to reduce "amp-glow" problems.
But full-frame cameras are risky for astrophotography. Few scopes can delivery a flat-image field large enough to fill a full-frame sensor. My TeleVue requires a large-field corrector. I've got a PlaneWave 12.5" CDK on order (PlaneWave can project a flat field roughly 70mm across). I don't use the full-frame camera in very many scopes -- usually using the Canon.
But I also have the ASI174 ... that camera has a smaller chip, it's also a "cooled" camera, but it's monochrome. The main reason I bought it was for solar imaging through my Ha solar telescope (Lunt). The camera has a "global" electronic shutter. Most cameras have "rolling" electronic shutters which means the read-out happens row-by-row. A "global" shutter camera can read out the whole sensor (all rows) in parallel. This gives it a very fast frame rate. At full resolution it can do 162 frames per second. In planetary and solar imaging, you typically shoot a few seconds of video frames and stack those (it's very different than deep-sky astrophotography). A solar Ha telescope is monochrome anyway (it only allows the 656.28nm band to pass ... so you see just one color... red). For solar Ha imaging there's no point using a color sensor (and you can't have CA when there's only one wavelength of light).
I can use it for color imaging by using the filter wheel. A filter wheel is typically loaded with R, G, B, & L filters (L = Luminance channel and this is really just a filter that does UV & IR blocking but allows the full visible spectrum through.) You capture some sample data with each filter and then combine to produce a full-color image.
The ZWO cameras are dedicated astrophotogrphy camera that can only be controlled via a computer. The cameras have no controls on them of any kind (just a USB port ... and a place to plug in a 12v power source to running the cooling system.)
Most of the guys I know start with a Canon DSLR. Canon is pretty good about having an open SDK so any software developer can write software to control the camera. Consequently there is tons of software out there for Canon. Nikon opens the SDK if you own a D5xxx series or higher model, but not for the D3xxx series (there are those who have reverse-engineered the protocol to hack their way in). Consequently there's less software out there for Nikon. Sony is usually avoided because of their "star eater" problem. Sony "RAW" images aren't really RAW. They process out noise to get better scores and this results in faint stars vanishing becuase the camera though it was noise. So far as I am aware, there is no way to get around that problem with a Sony. (Some Nikon models also have the "star eater" problem ... but not all.)
If you want a "new" Canon camera that has been modded (since you can't buy a new 60Da anymore), look to Astro Hutech (hutech.com). They are an authorized Canon dealer ... but they offer to do the mod on a new camera and they'll honor the warranty. If you buy from anyone else and send it out for modification, you basically just blew the warranty by modding it.
I often have to shoot through light pollution filters (I prefer to avoid them becuase you get wonky colors when part of the spectrum is being blocked) but sometimes I have little choice. I've used the Astronomik CLS filter in the EOS-Clip version (designed to clip into EOS APS-C cameras). They make CLS and CLS-CCD versions. The "-CCD" version is meant for cameras that have NO filtering at all (not even IR). The CLS version assumes the camera still blocks IR.
I have a few ways of imaging.
I do own a tracking head (Losmandy StarLapse system) which I bought specifically for "travel" (I can take in on an airline ... where I wouldn't trust the airline baggage handlers with my telescopes). When I do this, I typically use an intervalometer to run the bulb-mode and the images are call captured to the memory card. I unload them later when I'm ready to process.
But when I use a telescope, I usually either use a StellarMate appliance OR I use image capture software on the computer. In which case the images are captured to the computers and not the memory card.
For PC users of Canon cameras, "Backyard EOS" is the popular program to remotely control camera image-acquisition. I don't use a PC, but on the mac it's "AstroDSLR" that does this (there are many choices, but that's my favorite). It's made by cloudmakers.eu.
But I also use a StellarMate appliance. This is a Raspberry Pi (a Raspberry Pi is a tiny single-board computer about the size of a deck of playing cards). It controls EVERYTHING. It's crazy how automated it is.
If you had a permanent observatory (I do not) you can tell it what targets you want to shoot on the following night (you do this in the middle of the day) and do the image "sequencing" (tell it how many of each type of image to capture, etc.) and then just start it running.
What do you do? You go to bed and wake up in the morning to check your data. Honestly ... it feels like cheating.
The list price of the Raspberry Pi computer is $35 USD. that doesn't include the case, power supply (it runs on a 5v 2.5a power supply ... basically what you might use to charge a cellphone), or memory card (a 32GB memory card is less than $15). The StellarMate OS software is $50. You can buy the whole package as an appliance for $150 (but I already had a Raspberry Pi so I just paid the $50). The appliance version comes with a bunch of accessories.
When I use just the camera (tracking head) I'm often using my Canon EF 135mm f/2L USM. But I do have several other lenses. I don't have to worry about exposure duration because my camera is tracking and I'm not including landscape.
It is easier to learn with shorter focal lengths (I know guys who have tried to learn by going staright for a big SCT with a long focal length (e.g. 2000mm or longer) and that's tough. Long focal lengths will show every mistake.
I do most of my processing with PixInsight (€230 - works out to around $260 USD depending on the exchange rate) and then finish it with Lightroom & Photoshop.