alexbb

The significant difference comes from the low read noise and the recommended typical usage. With a CMOS sensor camera you'd probably want to take more shorter exposures. The mono Panasonic sensors found in the ASI1600/Atik Horizon/Qhy163 has a full well of ~20000 electrons which is converted by the ADU to a value represented on 12 bits (0-4095). Using a gain for the highest dynamic range, the ADU will indeed limit the resolution of read data. But for the highest dynamic range, the read noise is highest and this is not the best way to use such a camera. As I said in the beginning, with these CMOS sensors, for optimal results you should increase the gain - in order to benefit from the lower read noise. This also decreases the dynamic range. For an ASI1600, above a certain gain the dynamic range decreases enough so that the recorded data can be represented on a 12bit integer value so the ADC is no longer the limiting factor. What you need to do is to record as many exposures as you can. Be aware that compared to the typical usage of a camera with a CCD sensor with long exposures, a sub taken with a CMOS sensor will be much darker and a stack of subs as well. In order not to lose relevant data, make sure that the stack is represented on at least 32 bits. Some applications (ie. Registar) doesn't work with 32bit float fits files, but most of them do (PixInsight, APP, GIMP 2.10). If you want a comparison, is like having a cup filled with water (stack of long exposure CCD subs) or the same amount of water in a bucket (same amount of hours stack of short exposure CMOS subs) - the water will have different heights.

This is very nice!

Hello all, I'm in a quest for finding a used 120ED, but if I'm not lucky enough, I also consider buying a new one, sacrificing some other planned/unplanned astro acquisitions. My dilemma is about the flattener. I know the flatteners look alike for the 80, 100 and 120 ED scopes, but I don't know if there's a difference between the one for the 80ED and the one for the 120ED. Both scopes are F/7.5. Usually, universal flatteners work with a longer backfocus with a shorter FL scope and the backfocus distance decreases as the focal length increases. The reducers/flatteners dedicated to the 80 and 120 both work at a 55mm backfocus distance. Did anyone try an 120ED with the flattener dedicated for the 80ED? Or does anyone if their optical formula is different? I already have a flattener for the 80ED, but if I really need the flattener for the 120ED, I'd rather buy the scope and the flattener together from the beginning. Also, did anyone try the 120ED with another flattener? Thank you for your time! Clear skies! Alex

Perhaps you have some floppy dust bunnies bending the other way under gravity pull

But why rotate the camera? Better rotate the tube in the rings, you don't need to get any extra item.

The 72mm lens gathers less than 2.5 times the light the 130mm mirrored system does, even considering the light loss due reflectivity and central obstruction (I considered 92% mirror reflectivity and 8% light loss due to central obstruction). I would not bother.

One could hope hoped. The picture displayed red lockers, symbol for the EC versions. Perhaps the new iPolar adds significant to the cost and you also pay more for the portability. The CEM60 + a Berlebach tripod becomes more appealing. Back to the drawing board.

I spotted this before I saw your announcement. Is the CEM40 in the link the non EC version? Its price is just a tad lower than the CEM60's (without tripod). I hoped for something in the middle between the CEM25P and CEM60. ?

Edit: announced already on another topic

Thank you, Mark! My mount performs poorly and I can't take more than a few seconds unguided shots without trailing. I used a laptop for guiding and also for exposures control.

Or stretched more, but resolution lowered.

As usual, more colour

Thank you all so much!

Thank you, Ruud!

Recently I bought a Canon 6D for daytime photography. Of course I was going to put it one day behind a telescope. Said and done. Last weekend I went to my girlfriend's parents' village (Clear Outside estimates an SQM of 21.9 there), I put the Canon 6D behind the Esprit 80 and both of them on top of the tuned AZ-EQ5. Guiding was done with a finder guider and overall stayed at 1.5"-1.8" RMS. But the 6D has large pixels and I also downsampled the final image so there shouldn't be much loss due to poor tracking. Moon was rising just before 11 so I started early, shooting Orion as the first panel. 2 other higher panels followed, consisting of 21, 21 and 19 subs, 5 mins exposures at ISO1600. For the Orion's core I used also 12x5s. That's a total of 3 hours. The stars towards the corners are not perfect with the Esprit80 and a full frame sensor, but resampling at 60%, I do not notice any weird shapes. Can't wait to shoot a wide Antares region with this setup. On astrobin: https://www.astrobin.com/393580/ Clear skies! Alex

Can't wait to replace my AZ-EQ5 with one of these

Translating from pixels into arcseconds, it means ~2.3"-3.0" at a 1.16 arcsec/pixel scale.

With a 150PDS, 0.9x SkyWatcher coma corrector and ASI1600 I got these days 2-2.6 px fwhm. Guiding through OAG went smooth at 0.4-0.5" rms, with occasional variations to 0.35" or 0.6" rms, probably depending on seeing. Subs were 300s long. But my mirrors are new, the secondary even replaced with a larger one. Maybe your mirrors' coatings are too worn and light is spread in all directions.

This one https://www.firstlightoptics.com/adapters/lynx-astro-m48-adapter-for-sky-watcher-72ed.html Indeed, that should allow for a more inward focusing.

Hah! Did I miss that?

Hello, Steve! Maybe I pixel-peep, but the 0.85x SkyWatcher reducer/flattener and the OVL non reducing flattener don't give perfect results around corners with APS-C and 4/3" format sensors at the expected 55mm backfocus distance. I found that the image quality improves at ~60mm, but with the mentioned flatteners, at 60mm, you're just at the focus limit and stars are still not perfectly round at corners. Increase the backfocus distance more, and you won't be able to focus anymore. Here's an image shot with a Canon 550D (APS-C sized sensor) at 55mm backfocus (just the M48 -> EOS adapter used) and the SkyWatcher flattener. And below an image shot with the same flattener, but this time with a "spacer" about 3mm wide. The stars have a better shape at corners, though not perfect. And here's an image shot with an ASI1600 (4/3" sized sensor) at ~60mm backfocus, same flattener. The sensor is smaller, but the pixels are smaller too so they should emphasize any distortion. How good is good enough? That depends on each person. I don't think there's anything wrong with the optics, just that the backfocus distance should be more than 60mm and there's not enough focus travel distance to play with with those flatteners. One day I will try the TS as it seems that one is (or can be) fully inserted in the drawtube. Of course, I will post the results. Hope this is useful! Alex

Great entries so far! I hope you won't mind if I have one image containing data from both 2017 and 2018. Not really sure if I'd choose the same 5 every time, but here they are. Please click on them to see the acquisition details. M31 - Andromeda - with the Esprit 80 and 130PDS. Heart and Soul in RGB-HOO Veil super nova Great Orion Nebula - RGB + iR Crescent and surroundings

I should've posted some images made with the 130PDS here too. I'll just link now to the last one. I must admit that the SW coma corrector does add some extra halos and I must invest in a Baader MPCC. I found that I need some extra adapters for my current setup in order to screw the CC inside of the focuser with an adapter instead of just putting it in an eyepiece holder. Neither the ASI1600 + the ZWO filters help too much. Besides the occasional halos resulted when a bright star is nearby, I get microlensing halos too. I'll just have to live with this for a while. The Orion nebula shot with the 130PDS at the beginning of the Orion season:

There are a few posts of mine where you can see how the field looks at 55mm, both with the OVL non reducing flattener and the SkyWatcher one. Both need more than 55mm of backfocus, I found ~60mm as acceptable. I used the SkyWatcher one more often and I focus at between the center and a corner, somewhere at 1/3 of the distance, away from the center to have a better performance at the corners without any noticeable loss at the center. I measured the focal length with the OVL non reducing flattener as ~430mm and the focal length with the SW one as ~375mm. Both at ~60mm backfocus. With the SW flattener and 60mm backfocus, I can barely reach focus at infinity.

Me too!