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Clip-on filters for IR and Astro on full spectrum

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Tricky01 View Drop Down
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Post Options Post Options   Quote Tricky01 Quote  Post ReplyReply Direct Link To This Post Topic: Clip-on filters for IR and Astro on full spectrum
    Posted: 16 July 2021 at 14:17
I'm having my A7R modified to remove the IR/UV filter so I can have a play at some infrared imagery. Rather than have a fixed filter added I'm going the route of it being full spectrum and then using clip-in filters from the likes of STC or Astronomik. A brief search of the forum I couldn't find any reference to either. Might be my inability to search this forum well (STC returning lots of mentions of poSTCards and fellow dyxummer weSTCoast ), but thought I'd throw it out here.

So, my questions are:

1. How have people who use these filters found them? Any issues or drawbacks? Any things to be aware of by brand?
2. For infrared (probably 720nm), any brand recommendations?
3. For night sky, again any recommendations?*

*this last point has taken me down quite the rabbit hole across many astro forums where this is discussed. I'm not currently planning on delving too far into true astro photography (images of nebulae, star tracking mounts etc.), more looking at catching better images of milky way and starry nights. As I understand it, at minimum I'd need to re-add the IR/UV filter to avoid 'star bloat', but rather than going that route, I suspect a light pollution filter which also filters out >700nm would not only avoid the 'star bloat' but also provide better images of the night sky overall. The ones I've been looking at are:
A) STC astro nightscape
B) STC astro multispectra
C) Astronomik CLS-CCD

From what I can tell:
The Astronomik only lets through roughly 450-520nm (to allow 486nm H-beta and 496 & 501nm OIII) and 640-690nm (to allow 656nm H-alpha). All other wavelengths are filtered out.

Both STC astro filters filter out the same wavelengths, just with the multispectra getting transmission of removed wavelengths closer to 0% transmission, vs circa 30% for the nightscape. But the STC bands have more peaks and troughs. From what I can tell, STC lets through roughly 400-430nm, 440-540nm, 550-570nm and 640-690nm. I *think* allowing through 550-570 is to let through the green of aurora borealis (558nm), but not sure about the others.

Apologies, a lot to unpick there, but ultimately I'm trying to work out which clip-in filters are best. I suspect I should probably point some of the above questions to the astro forums I've discovered, but before I demonstrate my naivety in a new world of experts, I thought I'd approach it here first
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A7iii, A7R, 12f2.8, 15f2, 16-35f4, 35f1.8, 50 1.8, 85f1.8, 135f1.8GM, 100-400GM, 200-600G, 1.4xTC // A mount: Sig90f2.8 and Sig180f3.5 Macros
 



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nandbytes View Drop Down
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Post Options Post Options   Quote nandbytes Quote  Post ReplyReply Direct Link To This Post Posted: 16 July 2021 at 14:50
Firstly have a look at Kase filters
https://kasefilters.com/sony-alpha-clip-in-filters
they are cheaper but won't help you with IR.

Tbh I am not sure light pollution filters will help much if at all. Cities are swapping from sodium vapour bulbs to LED bulbs which have a very wide spectrum. You have seen my Stonehenge shots recently, on the UWA shot the light pollution to the left caused by Salisbury is mostly white in colour (in real life too!) instead of the yellow-ish glow from old sodium light. What happens if you cut out white light? elementary physics will tell you you won't have much left

Anyways yes astro is a MASSIVE rabbit hole. After going very deep into it I have managed to pull myself out.
I have decided to take it in (baby)steps, learning plan:
1. Find good dark sites, plan Milky Way shots using various apps etc
2. Take good single exposures of the milky way i.e. execute the above plan
3. Stack a small set of images to get better more detailed milky way and less noise. Also learn stacking, PP skills using various software and workout a good work flow.
I am currently at executing step 3.

4. Do milkyway panos with stacking.
5. Use stacking to photograph deep sky/space objects (or ones that is easy enough to do using stacking only)
6. Buy a MSM tracker and learn to use the tracker for milkyway.
7. Workout a good tracker setup that works for me.
8. Use tracker for deep space objects
9. at this point I will probably start looking at my gear to see how I can improve my images. this is really far away in future stuff so let's get to 8 first.

I have always wanted to try clip in filters for IR but never got round to it. I'd be very interested in hearing your findings on this matter.
As for UV/IR clip filter I once briefly discussed an this with Alan Burch (https://www.infraredcameraconversions.co.uk) and may be you can execute it. Basically once Alan removes the hot filter for you its large enough to be cut up and placed in one of the clip in filter holders (of course you'd have to remove the glass that it comes with). So may be work with Alan to see if it is possible to make a clip in filter out of Sony's hot mirror which would make it a truly convertible IR and normal camera which would be amazing.

Let us know how you get along generally speaking
my flickr
A1, A7C
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rastapartaman View Drop Down
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Post Options Post Options   Quote rastapartaman Quote  Post ReplyReply Direct Link To This Post Posted: 16 July 2021 at 18:09
Hi
I have a IR cut strong filter from the Minolta Dimage 7. I'll be in Twyford next Thursday and can take it if you want to give it a try. Still have to find it first. I believe it's a 62 or 67mm
Don't think, Just click it!!

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Tricky01 View Drop Down
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Post Options Post Options   Quote Tricky01 Quote  Post ReplyReply Direct Link To This Post Posted: 16 July 2021 at 21:33
Originally posted by rastapartaman rastapartaman wrote:

Hi
I have a IR cut strong filter from the Minolta Dimage 7. I'll be in Twyford next Thursday and can take it if you want to give it a try. Still have to find it first. I believe it's a 62 or 67mm
thatís very kind of you but I donít have the camera back yet. I think clip on will be my best bet though and give me most flexibility with lenses too.

@anand, thanks for your thoughts and I like your planning of Astro development, wise to have a toad map. Talking to Alan of infrared camera conversions.co.uk though it sounds like heís had joy with full spectrum and 200-600 without any filter so might just get an IR 720 to start and add an Astro filter if I find I need it.
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A7iii, A7R, 12f2.8, 15f2, 16-35f4, 35f1.8, 50 1.8, 85f1.8, 135f1.8GM, 100-400GM, 200-600G, 1.4xTC // A mount: Sig90f2.8 and Sig180f3.5 Macros
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