16 replies to this topic

[Solaris75]

I'm just getting into astrophotography and I'm planning on having multiple OTAs for various imaging scenarios. But everything I'm buying for this project, with the exception of the OTAs themselves, is supposed to be cross-compatible with room for growth. For instance, I got a harmonic mount and Tripod that's capable of handling way more weight than my current OTA requires. I bought an Eagle5 Pro computer that has way more computing and storage capability than what I think I'll need for a long time. In essence, I'm trying not to limit myself by avoiding performance choke points more restrictive than the OTAs themselves.

Now for the camera...

My current OTA can illuminate an APS-C sized sensor with only minor vignetting. But my next telescope I'm thinking of, could make use of a full frame sensor. I've been using astronomy.tools to determine what pixel size to use and I've decided that I can make use of a 3.76um pixel size with either setup. So my question is only with regards to sensor size vs image circle.

Here's the question:

Is there any reason I couldn't use a full frame sensor camera with my current OTA that produces a smaller image circle, knowing it'll vignette like heck, but just crop the pictures down to what an APS-C sensor would provide?

Thanks!

[hyiger]

In this case flats will remove some of the vignetting and the rest can be cropped out. Not sure what your budget is but full frame (unless you are using an existing DSLR) is a lot more expensive than APS-C. Also FF is more sensitive to tilt and back focus. You can use the field of view calculator in Astronomy Tools  to compare the differences between APS-C and FF for various targets. 

Edited by hyiger, 23 March 2025 - 12:36 PM.

[Alex McConahay]

The image made by the middle of a full frame camera is identical to the image made by a smaller sensor camera (not counting that you may have different size pixels). So, a cropped full frame image is identical to a full size from a smaller sensor using the same optical path. 

 

You waste money by buying more sensor than you need. But, you waste money buying a smaller sensor and then RE-BUYING a full frame later when you upgrade the tube. 

 

And remember, that bit about pixel size counts.

 

Alex

[Solaris75]

Okay! Thank you! My intention for now is to use one telescope at a time on one mount with one computer and with one camera. Literally just swapping scopes as I see fit depending on the target. I just wanted to make sure I can get as much out of each scope as I could get. Sounds like I'm about to buy a rather expensive SkyEye62. Thanks for confirming my suspicions, fellas.

[MartinNI]

Remember, the camera technology and computers and software changes faster than the other stuff.

[Solaris75]

Yeah, that's actually a big part of why I'm really stretching myself trying to get the very best tech I can afford. Trying to "buy once, cry once" so I can stay as capable as possible for as long as possible without buying some optical monster like a 14" hyperstar... which I very well may attempt to do some time in the next decade.

[Alex McConahay]

Remember, the camera technology and computers and software changes faster than the other stuff.

 

While I agree, unless you are truly chasing technology (something only the super rich and the super silly do) the difference between older equipment and this week's darling is not as much as you might think when it comes time to look at the pictures.  

 

Alex

[Robert7980]

I suppose it’s not a bad plan to save double investment if you plan of imagining in full frame to just deal with having to crop your projects on tubes that can’t illuminate it fully… 

 

I’d really want to research a lot before buying a large sensor, it may not be as useful as you think. APS-C isn’t at all terrible on many scopes where you are trying to reach out to the target. Full frame has more use for wider field shots with shorter tubes. The other reason it might be not be the ideal decision is the file size that’s produced which could drive the cost of everything else you need compute wise, more storage, more ram, faster CPUs… 

 

But if in your heart you’re set on FF, then just investing in what you ultimately want isn’t a bad idea, it’s probably smarter than investing in APS-C then investing again in a short time… Totally upto you, but I don’t see any real technical problems with it… 

 

I wouldn’t mind having a 6200MM, but the cost is prohibitively high for what I’d get from it, mosaics are always an option for ultra wide field if needed. So far I’ve not really run into a problem with APS-C not being wide enough… The cost of the 2600MM was enough for this guy, I did invest in gear and accessories that are FF compatible though so I can swap cameras out at some point if that math changes… But yeah owning two APS-C cameras definitely makes it less viable to invest in yet another sensor so going in once makes sense to me on some level…

 

The comments on difficult to setup are no joke, getting an APS-C dialed for backfocus and tilt can cause one to tear their hair out, FF will be all the more harder. So the optics and hardware need to really be on par, which gets more and more expensive the further you push it, not just the camera but everything else… Some of the tilt systems can set you back over a grand just on that one piece so…

 

Just know what you’re getting into for the complete system, the camera itself is probably the least important part to consider. Things like larger filters, more capable mounts, superior optics and as mentioned above higher end computer hardware will add up rapidly… 

Edited by Robert7980, 23 March 2025 - 06:22 PM.

[StargazerLuigi]

Full-frame sensors require large (thus more expensive) filters.

There are scopes that can illuminate a full-corrected image circle for full-frame, but typically those are very expensive.

Neither of the above two are issues if you have the resources.

 

Robert7980 is correct. I've been struggling with correcting tilt and back spacing issues with APS-C. Those tiny pixels take no prisoners in exposing tilt and back spacing issues.

 

None of this is meant to dissuade. Just so you have awareness of potential difficulties. 

[Solaris75]

Oh my gosh. You guys may have successfully changed my mind. I was a bit concerned about the tilt issues before. Now I'm very concerned. Maybe I will just go with the Aps-c sized sensor and mosaic the targets if really necessary.

[radon199]

I would add that I think APS-C size is the target of a lot of manufacturers. There are a lot of scopes that are designed to illuminate this sensor well. You will find a number of scopes that advertise that they illuminate a full frame sensor, but that isn't always the whole truth and you will find that it might have strong vignetting while still technically illuminating it.

 

Second, not everyone is the same but I think for a lot of us our goals have evolved over the years, and the things we planned to do when we started changed as we got used to the hobby and figured out where out interests lie. This might mean getting more than one camera to match well with the kind of imaging you want to do.

 

Also, going for a 6200 instead of a 2600 you are more than doubling the price for only 1.5x the pixels, to me it isn't worth it, but I don't know what your money situation is like and there are also people with $20,000 scopes on this forum that are happy and probably swear by them, so to each their own.

[Robert7980]

Oh my gosh. You guys may have successfully changed my mind. I was a bit concerned about the tilt issues before. Now I'm very concerned. Maybe I will just go with the Aps-c sized sensor and mosaic the targets if really necessary.

I think that’s probably wiser, wasn’t trying to talk you out of it, just trying to fill gaps and avoid finding things out the hard way… APS-C isn’t really compromising much, it’s a decently large sensor that isn’t getting into the extremes that full frame and medium format can lead to. 
 

Ultimately I think it’s more about the quality of the camera and not so much its size. Low noise and high quantum efficiency are what you want before looking at the real estate… Bigger sensors are nice though all else being equal… The most important thing to me is quality, especially over quantity… The last thing you want is a giant system that’s built with poor quality components that make it difficult to use. Smaller, easier and premium quality are where it’s at unless you have a fairly unlimited budget.

 

For beginners this is even more the case. Heck we all want a 1 meter scope with a medium format science package attached, then there’s reality and getting the bank to agree to that 1.2 million dollar project for the backyard haha… 
 

Really understanding exactly what you want is not always straightforward and it’s easy to make expensive mistakes , so just keep pondering it and researching things. I wouldn’t necessarily give up on full frame just because of things said here, although I do think it’s probably going to lead to a higher chance of success at a more reasonable cost with more flexibility in the future. 

[dswtan]

All the right points have been made, but I'll just add that there is a feeling in the daylight photo community that anything but full frame (35mm) is suboptimal -- or worse. 

 

This is especially true of us old-timers who grew up with 35mm film. So APS-C (or even the 4/3 that I use -- IMX492) is best to be avoided and "full frame is the ultimate goal".

 

Astro is totally different (IMO). Full frame is a luxury -- very hard and expensive to achieve. It's nothing like daylight full frame, which is relatively accessible. Good on you that can and want to go to the effort of full frame. But there's a lot of good astro to be done with APS-C (and lesser).

[WadeH237]

Oh my gosh. You guys may have successfully changed my mind. I was a bit concerned about the tilt issues before. Now I'm very concerned. Maybe I will just go with the Aps-c sized sensor and mosaic the targets if really necessary.

This is an excellent decision.

 

The only suggestion I would make is to change the last sentence to: "Maybe I will just go with the Aps-c sized sensor and get a shorter focal length scope for large fields if necessary."

 

If you put your APS-C size camera on something like a RedCat 51, you will be able to frame nearly any target.

[Solaris75]

This is an excellent decision.

The only suggestion I would make is to change the last sentence to: "Maybe I will just go with the Aps-c sized sensor and get a shorter focal length scope for large fields if necessary."

If you put your APS-C size camera on something like a RedCat 51, you will be able to frame nearly any target.

Yeah, that's my intention exactly. Looking at a Draco 62 for the wide field stuff. I already have a Meade 8" F/6.3 wide field that I got 34 some-odd years ago when I was a teenager. I'd like to get them both working. The sct could end up being more trouble than it's worth but I'd like to see it through and finally have it accomplish some of the things I could only dream of doing when I was in high school. If it doesn't work out, so be it, at least I tried and all the rest of my gear can be used with other scopes.

[Cryhavoc38]

Remember one thing about a camera like the 6200...it allows you to switch between full frame and aps-c region of interest.

I was able to aquire a 6200mc pro in a package deal so I didn't have to make a decision about spending the cash on full frame versus the venerable 2600 series cams but I do appreciate being able to switch between full frame and aps-c at the touch of a button in the asiair app.

[flappah]

Both my scopes support full frame sensors but my end goal is to “only” own a 2600 series camera (currently gravitating toward a mono version). Right now I’m shooting with the 585 and 533 cameras so upgrading towards the 2600 series feels like a big upgrade. And also cost wise I think that full frame is a bit too far for me.

Edited by flappah, 24 March 2025 - 02:32 PM.