I just did first light on my (new to me) AT8IN.
Check out this single 10-second sub: https://dl.dropboxusercontent.com/u/634 ... Y8-10s.jpg
it is 10 seconds so tracking etc. should not be an issue.
Stars are weirdly shaped across the field. It doesn't look like coma (well some areas have coma and some do not).
My question for the experts - is this solely due to bad collimation? (I used a Kodak film can!) or is the focuser sagging and causing the sensor to be tilted? (I hate that)
Newtonian weird stars
- orly_andico
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Re: Newtonian weird stars
I am no expert.
Can it be due to pinched optic in addition to field not flat.
Can it be due to pinched optic in addition to field not flat.
Re: Newtonian weird stars
I ever encounted such problem and i didn't like it at all. all are diamond shape star, its collimation problem. how you collimate it, still very very hard to get round nice star with F/5 or lower f newtonian.
Re: Newtonian weird stars
Hi orly,
Here is 5.39min H-alpha single sub with 6" newtonian F/5. no coma corrector.
thanks
Kimo
Here is 5.39min H-alpha single sub with 6" newtonian F/5. no coma corrector.
thanks
Kimo
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- M27-5.39-Halpha- 6 newtonian F-5.jpg (47.66 KiB) Viewed 3807 times
- orly_andico
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Re: Newtonian weird stars
for me, mis-collimation and mis-focus is aggravated because i'm at f/3.0
collimation only by eye. waiting for laser colli to arrive.
collimation only by eye. waiting for laser colli to arrive.
Re: Newtonian weird stars
laser collimator will be no use for astrophotography collimation. i had it before and i never used it.
1: do both optics aligment with just dot on EP cap and place one large gray paper under secondary ,day time alignment--works perfect
2: collimate with ccd and reducer.
first start from large round star on ccd "out focus" and collimate secondary, gradually reduce star size and keeps on collimateing (now require very fine adjustment) until you are satsfied.
i think you have another problem is that your CCD camera may not give you good result as it is color.
QHY8. HA- 25%, SII 25%, OIII 75%, HB 75%. will require long axposure on HA and SII.
1: do both optics aligment with just dot on EP cap and place one large gray paper under secondary ,day time alignment--works perfect
2: collimate with ccd and reducer.
first start from large round star on ccd "out focus" and collimate secondary, gradually reduce star size and keeps on collimateing (now require very fine adjustment) until you are satsfied.
i think you have another problem is that your CCD camera may not give you good result as it is color.
QHY8. HA- 25%, SII 25%, OIII 75%, HB 75%. will require long axposure on HA and SII.
Last edited by kimo on Wed Oct 02, 2013 5:49 pm, edited 1 time in total.
- orly_andico
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Re: Newtonian weird stars
Yes I know the OSC is less sensitive. That's why I'm running the OTA at f/3.