M42 and some questions

CCD vs Film? Lots of time vs no patience? Alright, this is your place to discuss all the astrophotography what's and what's not. You can discuss about techniques, accessories, cameras, whatever....just make sure you also post some nice photos here too!
Post Reply
celeron787
Posts: 4
Joined: Sun Jan 12, 2020 2:30 pm

M42 and some questions

Post by celeron787 »

Gotten my star adventurer tracker recently, tested it out with the orion nebula.
Results was quite similar to my first M42 untracked shot with 390 light frames.
Taken under my block at Bukit Panjang.
How much more integration time do I need to get the horsehead?

Sony a6000
18-135mm lens
ISO400
Lights: 13 x 60secs
Darks: 10 x 60secs
Flats: 10
Bias: 10
Stacked in DSS and processed in StarTools

Image

Drift alignment was really a hit or miss for me. I only did alignment using an overhead star.
Sometimes able to get no star drift for 60sec exposure at 135mm with just pointing north using a compass. Sometimes I get star trailing which then I have to correct.
drift.jpg
Compared to other drift alignment tutorials http://www.cwjames.info/astro/howto/pol ... nt_ccd.htm, my trails are vertical instead of horizontal, is it because of my camera orientation? It's orientated in portrait format while pointed overhead.
Also my trails move in the other direction instead, is it because I pressed the button the other way round? I pressed the front button first for 30secs then the back button for 35secs.
In this scenario, the correction would be opposite right? Meaning the above south drift would be corrected by turning the mount clockwise, which seemed to work.

Any tips will be much appreciated!
You do not have the required permissions to view the files attached to this post.

User avatar
ivan
Posts: 278
Joined: Tue Jul 30, 2013 6:52 pm
Favourite scope: TAK-oyaki
Location: Toa Payoh

Re: M42 and some questions

Post by ivan »

I recommend you get at least 1.5 hours of integration time, more if sky conditions are suboptimal. 60 seconds for each sub is acceptable for Singapore skies. With your 13 mins of data, I can see a hint of the flame nebula appearing.

As for drift, you need to know where the N/S/E/W directions are on your camera. You can do this by gently nudging the lens towards the north or south, and see where the star jumps. If you nudge the lens north, you will see the star jump towards the south, and vice versa. Based on this, you can also figure out where east and west are, but remember that the relative directions of N/S/E/W in celestial coordinates is a mirror image of that in geographical coordinates.

Based on your drift direction, the vertical axis is the right ascension (East-West direction), and the horizontal axis of your frame is the declination. But without any other information (can't tell based on the front/back button, since I don't know whether it increases or decreases your RA tracking speed), I cannot tell you whether east or west points upwards or downwards with respect to your camera screen. You need to determine this by nudging the lens in the east/west direction and seeing where the star jumps, or stopping the tracking temporarily (in which case the star will drift in the westward direction).

If your star drifts SOUTH, then you need to turn your mount's polar axis towards the WEST. When viewed from the top-down, this means your mount head needs to turn anticlockwise, not clockwise. If you find that doing the opposite reduces the drift, you might have made a mistake in determining the directions. In which case, simply adjust towards the direction that reduces the drift.
Just a casual stargazer

celeron787
Posts: 4
Joined: Sun Jan 12, 2020 2:30 pm

Re: M42 and some questions

Post by celeron787 »

Thanks Ivan for the detailed reply. Seems like I have my directions mixed up, need to read a few times to wrap my head around it. Will attempt it a few more times to make more sense of it.

kochu
Posts: 806
Joined: Tue Sep 30, 2003 9:51 pm
Favourite scope: Sharpstar-107PH Triplet.
Location: Jurong West

Re: M42 and some questions

Post by kochu »

Hi Ivan . Glad to note that you have become a Celebrity. Congrats.
Kochu

User avatar
ivan
Posts: 278
Joined: Tue Jul 30, 2013 6:52 pm
Favourite scope: TAK-oyaki
Location: Toa Payoh

Re: M42 and some questions

Post by ivan »

celeron787 wrote:
Wed Mar 25, 2020 9:30 am
Thanks Ivan for the detailed reply. Seems like I have my directions mixed up, need to read a few times to wrap my head around it. Will attempt it a few more times to make more sense of it.
No problem. It's difficult to explain these in words, but my main tip would be to really familiarise yourself with the directions (N/S/E/W) when you're looking up at the sky. That way, no matter where in the sky you're pointing, you would have a rough idea of where each of the four cardinal points are.
kochu wrote:
Wed Mar 25, 2020 11:40 am
Hi Ivan . Glad to note that you have become a Celebrity. Congrats.
Kochu
Thanks Kochu. I think 'celebrity' is overstating it. But I hope it at least makes more people in SG interested in astro :mrgreen:
Just a casual stargazer

User avatar
Airconvent
Super Moderator
Posts: 5623
Joined: Tue Sep 30, 2003 11:49 pm
Location: United Federation of the Planets

Re: M42 and some questions

Post by Airconvent »

ivan wrote:
Thu Mar 26, 2020 1:51 pm
Thanks Kochu. I think 'celebrity' is overstating it. But I hope it at least makes more people in SG interested in astro :mrgreen:
Enthusiastic evangelists like you are getting so few these days, Ivan...keep it up! :)
The Boldly Go Where No Meade Has Gone Before
Captain, RSS Enterprise NCC1701R
United Federation of the Planets

Post Reply