2" filters necessary for APS-C? - Forums

Hi all,

I'm curious to hear if anyone has successfully used 36mm filters for an APS-C sensor. I would like to upgrade to Astronomik MaxFR filters but I'd like to avoid shucking out $1300-1900 for the 2" filters if I can.

I have not used it with 36mm, but a 2" one that I think is equivalent to 42mm.
And thinking logically, you could use it without a problem, but you would have 2 cons. There would be more vignetting, and less light would enter. This depends on how much difference there is in mm the filter with the lens.

Yes, 36mm filters work with APS-C. I use 36mm filters with my ASI2600MM Pro, APS-C.

They absolutely work. I have been using 36mm filters with my QHY268M for a couple years now without issue. I guess you could have an issue if you have a configuration that puts the filters farther in front of the sensor than most common filter wheels do. I don't see any vignetting in my setup.
CS
Jeff

I also use 36mm filters with my ZWO 2600MM. No problems, just make sure you put the filter wheel next to the camera.

Good points on filter position. I have my EFW bolted to the camera and the ZWO OAG-L bolted to that. Add a 0.6mm shim and it's all set (my filters are 2mm thick).

I'm using 36mm filters with APS-C IMX571 camera with no problem of vigneting.

It also depends on scope speed… and your mounting distance from sensor to filter.

What may work for one may not work for another.

The maxFR filters are awesome by the way.

Josh Jones:
It also depends on scope speed... and your mounting distance from sensor to filter.

What may work for one may not work for another.

The maxFR filters are awesome by the way.

Yes, I’m realizing now that folks may not have realized I posted this in the Epsilon 130 forum. I should have specified in the title that I would like to know if anyone has paired 36mm filters with an APSC chip on the Epsilon (which is f/3.3). I know 1.25” filters did not work for me even with a 4/3 sensor on the Epsilon.

https://astronomy.tools/calculators/ccd_filter_size

At least you can calculate what should cover... but flats can help as well. Just depends if you need 100% max coverage... calc does a good job.

Josh Jones:
https://astronomy.tools/calculators/ccd_filter_size

At least you can calculate what should cover... but flats can help as well. Just depends if you need 100% max coverage... calc does a good job.

Not sure I can put much stock in this calculator. According to this I would need a minimum of 33mm. However, I did the calculation for a 4/3" sensor and it says for that I would only need 28mm. When I did try to pair 31mm filters with a 4/3" sensor on this scope there were crippling reflections.

Not sure I really understand… I don't know the distance you were using to calculate, obviously a 28mm filter right up on the sensor would cover it, but if you have 12.5mm backfocus + say 5mm or so for a filter, that would put it out at around 17 or 18mm away from the sensor you would need around 32-33mm for an Epsilon 130 and 4/3 sensor correct? That's obviously 100% coverage at that size, so might explain why 31mm filters you got some issues. reflections? or vignetting?

36mm filters would cover unless you started moving them really far out, like over 30mm away from sensor. 2" isn't necessary if you keep it up close. but maybe I'm missing something?

Yes, I’m realizing now that folks may not have realized I posted this in the Epsilon 130 forum. I should have specified in the title that I would like to know if anyone has paired 36mm filters with an APSC chip on the Epsilon (which is f/3.3). I know 1.25” filters did not work for me even with a 4/3 sensor on the Epsilon.

I use 36mm mounted filters on my E-160 and they are marginal requiring some cropping on a couple corners. My CFW doesn't exactly center the filters which is likely the problem - if it centered them properly I probably wouldn't need to do any cropping. I use a QHY268 with the QHY CFW3 bolted right on the camera so the filters are as close as I can get them.

I'm using 36mm filters with APS-C IMX571 camera with no problem of vigneting.

I use 36mm Astrodon filters from my two old STT cameras with two 571 based cameras (ZWO and Moravian). They are fine. Also, I just got the Moravian and bench tested it and it is very well built and makes the ZWO look like cheap Chinese crap....

Yes, I’m realizing now that folks may not have realized I posted this in the Epsilon 130 forum. I should have specified in the title that I would like to know if anyone has paired 36mm filters with an APSC chip on the Epsilon (which is f/3.3). I know 1.25” filters did not work for me even with a 4/3 sensor on the Epsilon.

I use 36mm mounted filters on my E-160 and they are marginal requiring some cropping on a couple corners. My CFW doesn't exactly center the filters which is likely the problem - if it centered them properly I probably wouldn't need to do any cropping. I use a QHY268 with the QHY CFW3 bolted right on the camera so the filters are as close as I can get them.

Thank you. Have you looked into third-party filter-centering masks?

Bill McLaughlin:
I'm using 36mm filters with APS-C IMX571 camera with no problem of vigneting.

I use 36mm Astrodon filters from my two old STT cameras with two 571 based cameras (ZWO and Moravian). They are fine. Also, I just got the Moravian and bench tested it and it is very well built and makes the ZWO look like cheap Chinese crap....

Mine is not a ZWO, I don't like ZWO they put their custumers in jail !

I moved from a Risingcam 571c with a 2" filter in a drawer to a 571m with 36mm unmounted filters on the 130D. My LRGB calibrated files are tending to look like this:

I'm not sure if it's explicitly a filter vignetting issue or a focus shifting between lights and flats issue but it would probably be avoided with either a camera with less focal flange distance or larger filters.

I moved from a Risingcam 571c with a 2" filter in a drawer to a 571m with 36mm unmounted filters on the 130D. My LRGB calibrated files are tending to look like this:

I'm not sure if it's explicitly a filter vignetting issue or a focus shifting between lights and flats issue but it would probably be avoided with either a camera with less focal flange distance or larger filters.

I would think flats would correct that. The vignetting doesn’t look bad at all in either case.

This is in fact a calibrated image - there's no clear hard vignetting in the uncalibrated file but there's clearly some sort of filter related calibration problem.

I haven't nailed down the cause but I suspect either shorter backfocus camera or larger filters would mitigate the problem entirely.

Or maybe I'm barking up the wrong tree and there's a entirely unrelated cause.

Your calibration isn't working right. See that embossed donut? That's indicating your filter is not in the same position during flats as it was during lights. Make sure you're using uni-directional on the filter wheel. That will eliminate the problem

I moved from a Risingcam 571c with a 2" filter in a drawer to a 571m with 36mm unmounted filters on the 130D. My LRGB calibrated files are tending to look like this:

I'm not sure if it's explicitly a filter vignetting issue or a focus shifting between lights and flats issue but it would probably be avoided with either a camera with less focal flange distance or larger filters.

I would think flats would correct that. The vignetting doesn’t look bad at all in either case.

I have exactly the same setup and both RisingCam 571. I think something is going wrong on yours. The donut is just a dust that can be solve by flats. But the top angle tend to prove some misalignment in the optical train. It could be a bad secondary miror positionning.

That dust spot actually showed up *not* on the filters, I think it landed on the back of the CC. Not the issue.

I'm fairly certain it's just the filter wheel misbehaving - Johnny Bravo's suggestion to "force" unidirectional filter wheel movement may have fixed it.

Just bite the bullet and buy the 2" and get good ones so you don't need to buy them twice.
Then you'll also be good if you ever get a full frame chip.

I ended up getting comet stars at the corners if I didn't use 2" filter..learned the hard way after messing with 2600mc pro sensor alignment… luckily was able to level reset the sensor and now using 2" filter works wonders.

Edit:
Should've said that I was using 1.25" filter which resulted in comet stars with aps-c sensor. Which is why 2" filter helps.