First Light with new ASI585MC Pro.: Page 2

First Light with new ASI585MC Pro.

Kevin_A

w7ay I found that this lens is very critical for backspacing. So much that I use a vernier to measure the stack of parts. Even having filter changes that are 1.85mm vs 2mm is enough to have to change my shims.

w7ay

Kevin_A Even having filter changes that are 1.85mm vs 2mm is enough to have to change my shims.

The FSQ-85 is sensitive to even 0.1mm of backspace too (if you care about getting small stars) for Takahashi's native 56.2 mm number. (I have not yet figured out why such weird backfocus number, but it is uniform for all of their FSQ flatteners and reducers; and they are serious about the "0.2mm" part :-).

I have a couple of sets of the Agena Blue Fireball metal spacers that go from 0.1mm to 1mm in 0.1mm steps to handle the Taks. None of the silly 3D printed spacers (and Baader's metal spacers don't have enough resolution); thank god for Blue Fireball (Agena house brand?).

https://agenaastro.com/blue-fireball-9-pc-fine-tuning-spacer-ring-set-for-m54-threads-0-1-to-1-0-mm-s-set9.html

Their M54 tube spacers are also quite good -- threads almost as smooth as the custom stuff from PreciseParts.

Heavier clouds came in by the time Corona Borealis appeared over the tree tops, so never got to take my pre-Nova reference photo.

The price vs sharpness is fabulous to say the least.

I concur. This appears to be one sharp lens for its price (especially after having gone through Canon-L and Sigma-ART lenses). I tried both f/3.85 and f/2.9 last night, and the f/2.9 does not appear to suffer much at all from f/3.85 for APS-C frames. (Weird numbers are from step down rings and the camera filters after removing the glass.) Its usefulness is somewhere between APS-C and full frame (I was testing with an ASI6200MC). I might stick to f/2.9; less than 1/2 stop difference though, FWIW.

Chen

Kevin_A

w7ay I ended up settling on f2.8 after all my testing. I would have liked to have gone to f2.4 but it started looking a bit off. Another cheap but fabulously sharp coma free, astigmatism free lens is the Tamron SP 35mm f1.4 lens. I was hugely impressed and found it so much better than the Sigma A 40mm f1.4 lens at way less of a price. I am now in the process of buying a SW Esprit 100ED scope for deep space targets as it seems very nice too.

w7ay

Kevin_A Tamron SP 35mm f1.4 lens

As long as it is not Chinese glass, I am willing to try :-).

My trees would only allow something like 1/2 hour exposures for 35mm type focal lengths, though. I have the Samyang XP 50/1.2 for meteor showers, and for that, I don't even track. Just point to a clear spot in the sky. Might be able to do the same with a 35mm. I am not impressed with stars on the 50/1.2, so I am willing to try something else. 35mm on APS-C is not far from 50mm on full frame.

Chen

w7ay

Kevin_A Tamron SP 35mm f1.4 lens

Wait... can this lens be manually focused without being attached to an DSLR camera?

P.S. Back to the ASI585MC -- UPS says it is coming tomorrow. Yeah, snatched the last one from my favorite Seattle telescope store.

Chen

Kevin_A

w7ay I know the SP 35 says designed in Japan on it. With this lens on my Nikon Z7 I remove it from my camera while it is at f1.4 with the camera still on and it stays at f1.4. I shoot it at f1.4 as well as it is very sharp wide open.
Here is a low rez stacked shot of 30 minutes of 60s subs at f1.4 on a SW tracker and Nikon Z7.

w7ay

Kevin_A I know the SP 35 says designed in Japan on it.

Manual focus?

Chen

Kevin_A

w7ay both manual and auto. I always use manual. No VR so that is good too.

https://www.tamron.com/global/consumer/lenses/f045/spec.html#nav

w7ay

Kevin_A both manual and auto

OK, it is the next lens to look at after getting the Rokinon 135 optimized (using the English meaning of optimize, and not ZWO's usage of that term, which is a bug fix).

Perhaps get it ready for Perseids.

I have given up on the Milky Way from here. It is towards the south, and the sky pollution there is like a Bortle 8. I can get something like "looks" like the Milky Way, but nothing like what I saw as a kid in Asia.

By the way, even the ASI585 is good for a 4.7º x 2.7º field of view with a 135mm lens -- easily frames M42 and Running Man, not to mention M31. With slightly better pixel size than an ASI6200. Problem would be the dynamic range for M42 and M31.

Chen

w7ay

Kevin_A https://www.tamron.com/global/consumer/lenses/f045/spec.html#nav

Darn... just when I have started to standardize on 77mm filter thread (and step downs) as apertures for my lenses. :-).

Chen

Kevin_A

w7ay one thing I did notice with the cooled 585 was the amount of hot pixels at HGC. I used Unity gain 198 and it was reduced greatly but that 198 setting still seems to have a bit too little FWC for my broadband imaging and bright stars really got saturated fast at f5.6 on my 115mm triplet. I am going to test gain 150 as it seems like a good balance and the extra noise will get eliminated with more total integration. Using LGC has a normal amount of hot pixels, but HGC just goes nuts!

w7ay

Kevin_A the amount of hot pixels at HGC

Hope this is not a trend. There are already zillions of hot pixels in the ZWO 2600/6200/533 series. Have you tried gains pf 20dB to 30dB with those cameras? More hot pixels than bright stars :-).

Chen

Kevin_A

w7ay I tried at 25db and that was too much. This camera is worse at HGC than my 533 and 2600 cameras. I think with this 585 camera the FWC is so small at that gain that they just light up like Christmas from current leakage…. But who knows. At unity they are easily managed.
So I prefer to use where the FWC is fairly normal maybe at 15db and I can deal with the read noise with more subs and it will allow less saturation of bright objects too. Luckily my use is on smaller dim galaxies. Narrowband with filters may prove better with higher gains or Unity.

w7ay

Kevin_A I can deal with the read noise with more subs

Yeah, no other way around that :-).

My cooled ASI585 arrived this morning, but the clouds have not departed :-).

Chen

w7ay

Kevin_A I

OK, I just did a different Frankensteining... I mixed and matched end plates of the "new ZWO 54mm filter drawer" with a "new ZWO 42mm drawer." So now I have a Franken drawer with a 54mm hole, with a T2 male on the other end for the ASI585's native 11mm T2 ring.

I would still need the PreciseParts adapter when I need to use a 54mm Filter Wheel.

No clear nights in sight, according to Wunderground.

Chen

w7ay

Kevin_A

OK, Moon uncropped (but resized) single exposure through 455mm focal length and the cooled ASI585 (0 dB gain), with ASIAIR. Through thin clouds, 1 hour before sunset, just the IDAS HEUIB. Looks clean enough with such short (10ms) exposure.

I should try the camera on the FOA60-Q (highest Strehl commercial scope :-) at 901mm focal length; should fill the frame nicely, albeit with only 60mm aperture.

Pity it is a Bayer camera, otherwise I can try it too with Solar.

Should have a clear night on Tuesday.

Chen

w7ay

Kevin_A I tried at 25db and that was too much.

One hour before we leave astronomical twilight, the ASI585MC-Pro at Unity gain, 180 second. 455mm-f/5.4. Already quite noisy, but workable. Just average more frames.

Cooling of the small camera is no sweat at all. 8ºC ambient, -10ºC with just 25% cooler power consumption.

Chen

w7ay

My cooled ASI585 arrived this morning

More ZWO cables to add to the thrash. Sigh. Their cables even looks like garbage.

Swapped in my Frankenstein M54 female to M42 female x 11mm thick spacer on the ASI585 already :-). PreciseParts says it is shipping the proper 11mm adapter ring on Apr 18.

Chen

Kevin_A

w7ay looks decent!

Kevin_A

w7ay I am going to try mine on my new Esprit when it arrives soon!

w7ay

Kevin_A

Just tried unity gain -- oh boy , really noisy.

Chen

w7ay

Kevin_A I am going to try mine on my new Esprit when it arrives soon!

The nice thing about buying a Takahashi is you don't have to constantly "upgrade" the OTA :-). Saves money on the long run. I have yet to find any new 60-90mm scope that makes me want to open up my wallet. One of them needs to produce a chromatic spot diagram close to that from the Baby-Q (Askars are about twice the spot size, although the V series looks better).

If I could take the weight, I would get the real FSQ-106; but as it is, I can barely carry that scope without camera and filters, and that is too much of a hassle. I have set everything up so I can just plop my scoe on the mount and not even do a polar alignment.

Chen

w7ay

Kevin_A I

1/2 hour before leaving astronomical twilight; same settings as above. I guess the previous image included a lot of sky backgroud. This one looks more promising (M51 vs sky). The dark vignette is one of my antenna masts. Once it clears and I leave twilight, I can try some autorun in ASIAIR after refocusing.

Chen

w7ay

Kevin_A

Just left astronomical twilight (so not completey dark quite yet). Noise appears manageable with unity gain and 180 sec exposure (around Bortle 5 for that part of the sky with some high thin clouds).

"Feels" a bit better than my cooled ASI183MM.

Chen

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