22 replies to this topic

[Riaandw]

Looking for an Infrared sensitive camera recommendation. Sensor with good efficency further into NIR 950nm - 1200nm.

 

Most current cmos drop of rapidly around 900nm.

 

Anything not astronomically priced available to the amateur? 

[Phil Perry]

Many digital cameras intended for general photography include an IR rejection filter. Perhaps you can simply remove the filter? I don't know how far into the IR that will take you. Surveillance video cameras often have the IR filter removed for low-light capability, if you're looking for video.

 

Just watch out for SLO's!

[Riaandw]

Mmm, Zwo wants 15K for the IMX990

 

[Tapio]

Your title 'IR sensor for guiding'.
Are you thinking of ONAG solution?

ONAG SC costs about $1000 but maybe the IMX990 is still overkill...
But there are cheaper options with relatively good IR sensitivity.
Like this with IMX462 sensor:
https://agenaastro.c...-iii-462-c.html

"The peak QE in the NIR around 800nm is as high or higher as the peak QE in the visible wavelengths. "

[pyrasanth]

If your planning an ONAG then read the review on the ASI432MM- it is very suited to long focal length instruments which is the typical type of telescope used with the ONAG.

 

I had great results with the ASI174MM PRO as well but the 9um pixels of the ASI432 might give me food for thought to consider an upgrade especially as the sensor area is big which is more suited to the size of the ONAG XM guide stage that I use. The ASI174MM PRO is certainly sensitive for the ONAG- I get a lot of stars visible for PHD2 guiding so I suspect the 432 would be even better.

 

Do give consideration to your focal length vs the "right" guide camera pixel size- it is important for good guiding results.

Edited by pyrasanth, 26 May 2025 - 03:27 AM.

[Riaandw]

Indeed for the ONAG SC. 

 

Here's 120mc with IR filter removed. Not unusable and the result is acceptable. Looking at better options though.

 

And the 290c

 

676 looks good too.

 

462 family is also great and affordable. 

 

464

 

Would be great to see what the 174 looks like through the ONAG if you have a screenshot available.

 

Thank you for the pixel size reminder. I'll have to work this out. 

Edited by Riaandw, 26 May 2025 - 05:04 AM.

[Riaandw]

ASI432MM would double nicely for dual purpose planetary guider. And dipping toes in solar perhaps... 

[Riaandw]

Really shouldn't have. Crunched the numbers. ASI432MM has the lowest read noise as far as I know. 9x9=81/2.9e is only 0.035 electrons.

462/585/664 are all above 0.05 electrons mm2. 

 

676/678 a show stopping 0.14e.

 

The imx432 is way out of my budget currently.

Edited by Riaandw, 07 June 2025 - 07:00 AM.

[NuovaApe]

Sony Starvis have pretty good NIR.

I bought a cheap Svbony SV705C (IMX585 colour, Starvis 2) to play with NIR (1083nm).

 

At that wavelength each IMX585 R/G/B photosite has pretty much the same sensitivity, so you can essentially use it as a mono cam.

I used [R,G,B] capture gain of [128,140,150] in the capture software to get almost perfect grey. Or [1x, 1.09x, 1.17x] in relative terms.

 

I used a 980nm torch (ebay) as a test light source.

 

Rather than do "colour binning" in the camera or capture software, I played with it in post processing using SIRIL "Geometry / Binning". Pretend it doesn't have a Bayer colour mask and treat it as a mono image.

 

I pulled my SV705C apart to remove the sensor protector glass, to remove any IR blocking it might have.

It was hard - the SV is bonded together with "very sticky black gluey foam".

Undo the screws and try to "bend" the two halves apart. Eventually you'll hear the foam tear a little.

I think I used an Allen key/wrench to give me some leverage.

Work your way around. It gets easier.

 

To stop dust getting on the sensor face I bought a ZWO "T2 1.25 filter ring".

https://www.zwoastro...-filter-holder/

 

Put any filter you like in the middle part, then screw the thing into the camera nose.

Remove it when you need to use it.

 

IMX585C on Svbony website:
 

 

A test shot with the 585 + 1083nm filter (1.7nm bandwidth) + 8 second exposure...

 

 

Best, Ed.

 

Edited by NuovaApe, 08 June 2025 - 07:42 AM.

[AstroOlly]

Looking for an Infrared sensitive camera recommendation. Sensor with good efficency further into NIR 950nm - 1200nm.

 

Most current cmos drop of rapidly around 900nm.

 

Anything not astronomically priced available to the amateur? 

For this exact scenario you need the newer IMX462mm camera, it’s exactly for this purpose and is extremely sensitive in the IR end of the spectrum, I bought it for IR guiding with a ZWO 850nm IR pass filter, and it’s great, I use the Touptek version 

[Riaandw]

The only issue i have with the imx462 or 662 ia the sensor size @6.46mm diagonal a not a great match for the ONAG. It means I'll have to shift the sensor around to find good guide stars. I current have the same sized imx290 from SVbony and rarely able to use multi star guiding. I am not sure the infrared sensitivity of the 462 will improve this.

 

The 664 is also very sensitive beyond 700nm and 9.02mm

 

Any thoughts on the IMX482?

 

Or just get the tried and tested Imx585.

 

There seems to be no such thing as a all in one perfect fit.

 

 

The Imx676 has a larger square sensor @10.04mm and the pixel size will allow for planetary without a barlow at F10. The read noise concerns me. I would not be able to use it for DSO lucky imaging. Am I over stressing this?

[Riaandw]

 

A test shot with the 585 + 1083nm filter (1.7nm bandwidth) + 8 second exposure...

 

 

 

That is really impressive for 8 seconds. Would you say the seeing was good?

[NuovaApe]

It was reasonably stable, -2C°.

First time I looked at the moon through that C9.25 for 20 years though, so can't compare really.

It wasn't well polar aligned. There was drift during each 8s.

 

It was a stack of 5, not a single exposure.

Then gentle unsharp mask in GIMP.

 

I found this transmission curve regarding Celestron XLT coatings. Mine has Starbright.

https://www.research..._fig3_241553344

 

Edited by NuovaApe, 08 June 2025 - 11:30 AM.

[Riaandw]

That's interesting. I never thought to check the coatings transmission curve... Actually assumed it would be full spectrum. Let me see if I can find anything for the 14" ACF

 

Would be a waste to get a camera that can do 95% at 750nm if the corrector only passes 80%.

Edited by Riaandw, 08 June 2025 - 11:38 AM.

[Riaandw]

Well, if things couldn't get more confusing...

https://www.research..._fig1_377356462

[xonefs]

What's the use case for using an ONAG exactly with amateur equipment? What does that give you over just using an OAG?

 

Silicon CMOS sensors all don't perform well deeper into IR. It's a limitation of silicon itself and it becomes completely transparent further into infrared. SWIR cameras use inGaAs sensors and the construction of them is a lot more challenging and expensive. 

[Riaandw]

The ONAG is bit of a engineering masterpiece. The same benefits as OAG without any of the limitations. So immune to flexure and mirror flop. 

If your guide sensor is large enough there is no to ever rotate or adjust, it has the same view as the imagining sensor only in infrared. There is suppose to be a seeing advantage with infrared guiding too.

 

The IFI sharplock software allows for real time live autofocus. No need to stop imaging.

Useful range for the guide port is 750nm -1100nm.

 

Cons.

You're stuck beyond 90mm of back focus so reducers and extenders need to be carefully planned.

There is a possibility for internal reflections in the IR bandwidth. IR cut on imaging camera solves this.

Some say longer exposures. I do not find this to be the case. IMX290 with IR cut window removed sees guide stars 0.1s exposures. But the chip is to small to take advantage of the concept.

Works on all SCT's but some Newtonians might not have enough backfocus.

Edited by Riaandw, 09 June 2025 - 01:02 AM.

[xonefs]

Yeah makes sense I guess, I’ve mostly heard of them in professional observatories where it makes more sense to me. Seems like a big cost when the larger fov oags with big chip guide cams are more affordable and I haven’t run into many limitations with them.

[pyrasanth]

Here is a screen grab of the ASI174 MM on a 2x2 bin on the guide stage of the ONAG XM- so we have an effective pixel size of nearly 12 um. The focal length of the C14 is 2730 mm at F7.7 with the reducer.

 

This is a pretty poor pretty poor night, very hazy,  but there are lots of visible stars seen in the PHD2 view. It really is a great guiding camera.

 

[Riaandw]

Here is a screen grab of the ASI174 MM on a 2x2 bin on the guide stage of the ONAG XM- so we have an effective pixel size of nearly 12 um. The focal length of the C14 is 2730 mm at F7.7 with the reducer.

 

This is a pretty poor pretty poor night, very hazy,  but there are lots of visible stars seen in the PHD2 view. It really is a great guiding camera.

 

M57_ASI174_guiding.jpg

That is a rather inspiring view. I'll just have to save for a larger sensor then.

 

The reducer has plenty of backfocus I see. And with that in mind I assume you are using the native mirror shift focuser. Conventional thinking is that mirror sag on large SCT is an issue if not locked down. I am doubting this.With OAG and ONAD and we refocus every 30 minutes. Have you noticed any issues?

 

I have a crayford style on the Meade ACF and back focus available into the neighbor's backyard. But it does limit the accessories I can use to 2". The lumicon F4 Full Frame reducer for instance. So been thinking about getting a bracket and trying.

 

Thanks for the screen grab!

[pyrasanth]

That is a rather inspiring view. I'll just have to save for a larger sensor then.

 

The reducer has plenty of backfocus I see. And with that in mind I assume you are using the native mirror shift focuser. Conventional thinking is that mirror sag on large SCT is an issue if not locked down. I am doubting this.With OAG and ONAD and we refocus every 30 minutes. Have you noticed any issues?

 

I have a crayford style on the Meade ACF and back focus available into the neighbor's backyard. But it does limit the accessories I can use to 2". The lumicon F4 Full Frame reducer for instance. So been thinking about getting a bracket and trying.

 

Thanks for the screen grab!

The performance you see was forcibly taken with the mirror shift focuser and focused by eye then locked down with the Optec low profile mirror locks.

 

Let me explain "forcibly". I normally focus by keeping the mirror locked and using the Optec SMFS to focus by moving the secondary mirror. This "normally" means that the primary mirror remains locked at all times. Unfortunately the SMFS has developed a fault where is will not home so it needs to be repaired at the next opportunity.  

 

I'm fitting my backup focusing solution, the focus cube zero, which will not be a robust as the SMFS as I will need to focus by moving the mirror. This is okay provided you remember to lock the mirror before a meridian flip. However either focusing means can produce good results.

[pyrasanth]

I fixed the Optec SMFS. The focus position had somehow managed to go out of range- so I disassembled the ONAG and reset the position by hand to central in the focus range. This allowed the firmware to perform as expected. I think the issue was caused by a power interruption during homing so the next restart could not establish the middle of the focus travel which is where "home" is reported from.

 

I love the ONAG- it really is a spectacular guiding solution and as said earlier by another I also would be disappointed not to have the SMFS hence a priority to fix. 

[Riaandw]

Looked into the Optec SMFS. Why that's not the standard on SCT's is beyond me. Would love to add a little tip tilt image stabilisation to it...

 

Same here. I tried the giant easy guider again a few days ago. Massive prism and all. Not even comparable to the ONAG.

 

So, here is the canon 6d guiding in IR 750nm> through the ONAG untill we can get the guide camera issue resolved. 

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