El Cheapo Reducer

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Vesmaobs261
Posts: 23
Joined: Thu Sep 09, 2021 6:04 am

El Cheapo Reducer

#1

Post by Vesmaobs261 »

Hi guys and girls,
Here is M1 shot through my 7" Mak. with a
0.5 reducer that dropped the focal length from
2700mm to 1350mm. I bought the reducer because
it was going cheap and wanted try it out using
the above scope and an ASI224 camera. I didn't
have high expectations for this reducer to be
honest but curiosity as to how it would perform
drove me to buy the thing.
The image is a total of 45 frames taken at 30 sec.
each, at a gain of 400 with a master dark of 20
frames. The slight oval shape of the stars I'm
sure was due to an on and off breeze that buffeted
the scope during imaging.
For an el cheapo reducer I think it done a great job,
considering the filamentary structure visible after
only some modest processing, though further testing
needs to be done with the couple of other scopes
that I have, but coupled to the Mak. it's a winner.
Cheers and all the best.
George :D
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M1 El Cheapo Reducer.jpg
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oopfan
Posts: 1328
Joined: Sat Jul 08, 2017 2:37 pm
Location: New York
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Re: El Cheapo Reducer

#2

Post by oopfan »

Hi,

Impressive! Amazed that you located it with such a narrow field-of-view. Here is what I suggest:

Your gain is way too high. That's why you lost star color. At Gain 400 the Full Well Depth (FWD) of each pixel is only around 300 electrons (e-). At that gain, stars almost instantly saturate. I'm looking at the ZWO docs for the ASI224MC. Gain 100 looks to be a better choice: FWD of 6000e- and Read Noise of 1.35e-. Or you could go down to Gain 60: FWD of 10000e- and Read Noise of 1.6e-. Don't go lower than Gain 60 since your Read Noise will skyrocket.

I've had good luck with DSO's using planetary cameras. I like my 290-based camera when I need a small pixel size. Just be cautious in hot weather as thermal noise (dark noise) becomes a real problem with uncooled cameras. Keep exposures as short as possible.

Brian
Vesmaobs261
Posts: 23
Joined: Thu Sep 09, 2021 6:04 am

Re: El Cheapo Reducer

#3

Post by Vesmaobs261 »

Hi Brian,
Yeah, took a little bit of fiddling about but after several minutes
managed to get it onto the chip after a few nasty expletives using
muffled tones...amazing how that always works.
Thanks for the info.by the way, always good to get other
ideas that will bring about even better results.
Cheers
George :D
timh
Posts: 515
Joined: Mon Aug 26, 2019 5:50 pm

Re: El Cheapo Reducer

#4

Post by timh »

George, I think that Brian's comment is right per the stars but you did pretty well to get that good an image of M1 at that focal length in just 20 min and on a planetary camera -- good pointing certainly! Nowadays you can always take the stars out -- image them more appropriately and pop the better ones in place later on. Tim
Vesmaobs261
Posts: 23
Joined: Thu Sep 09, 2021 6:04 am

Re: El Cheapo Reducer

#5

Post by Vesmaobs261 »

Hi Tim,
Thanks for the kind words. I've mainly been an
observer ever since I caught the astronomy bug,
and it's only been about a year and a half that I
seriously decided to give imaging a try after seeing
what others were accomplishing with the same
equipment that I have. With the added info that
the more experienced imagers contribute to us
newbies it sure makes it fun, and challenging at
times to improve one's technique, even if it's only
a modest improvement.
Cheers :)
George
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