Need help on tracking of objects...long exposures...

[Jonarsh]

Hi guys,

I'm thinking of taking stuff like Nebulas, want to check if my setup will work?

I currently have a 5" Schmidt Cassegrain, Celestron CG-4 mount, I'm thinking of getting the dual axis motor drive to help me get long exposures. Will it work?? Also is there anything else I need such as half pier...autoguider?? or polar alignment scope? By the way Im using a Canon DSLR.

I'm going into Malaysia this weekend, hope to take something exiting!

* Jonarsh *

[orly_andico]

most nebulas are large. the telescope you have would have too high a magnification. Its focal length is very long, magnifying any errors in the mount.

your mount is quite basic. it would have large errors.

if you get the dual-axis motor kit, you would also need a GPUSB and mod the motor so you can autoguide. you would then need a computer and webcam for the autoguider.

all in all very complicated and not something you can assemble and learn to use quickly.

my suggestion - use the CG-4 with the dual-motor kit, but use a camera lens and not your telescope. if you have a 100mm to 200mm prime that would be great. if not... use a 70-300 zoom or similar.

[Jonarsh]

Thanks Orly! I will take your advice into consideration! )

[Jonarsh]

Ok! I just got my dual axis motor...now I need to learn how to do alignment... and hopefully use it to take some photos!

Any tips on doing alignment??

[cloud_cover]

Oh dear, I see no one has answered for a while.
Alignment for photography requires fairly precise alignment and is usually done by drift aligning.
http://www.astropix.com/HTML/I_ASTROP/TRACKED/POLAR.HTM
It does help though to be roughly aligned already before starting so keep a good compass and leveller ready! Of course visual use doesn't require such stringent alignment and a simple compass fix is good enough

[orly_andico]

maybe you should sign up for Remus' basic AP course tomorrow.. if there still are slots.

it's kinda hard to explain on a forum how to polar align. i'm no expert mind - but i have a dumb technique that seems to work well enough (and no I'm not using software anymore).

[MooEy]

Don't think so much of the equipment for now, practice setting up and drift alignment and take a few shots. Even the best equipment in the world takes lousy photos on first few attempts.

[shirox]

It took me a few sessions to figured out how to effectively do a drift alignment. As what mooey says, do more practice and get more field experience instead.
Information on the net on drift alignment can be confusing sometimes. Best is to join a group do AP together so they can guide you along the way rather.

[kochu]

It is not all that difficult to do drift align. Just try the following step by step.

Support items required.

1. Spirit level, 2 Magnetic compass ( Both these can be substituted with ipad or smart phone app)., 3 Illuminated reticle.

Procedure.

1. Place the mount facing Magnetic north using compass to the best possible way
2.Balance the mount in RA and DEc axes.
3.Adjust the RA axis to your latitude- Just about 1.5 degree for Singapore.
4. Turn the scope to South and stand facing south.
5.Adjust the mount so that counterweight is in 8'O ckock position. i.e to your left .
6 .Point the scope to a bright star located on Zenith to 15 degrees to south.
7.Put the star on the centre of one reticle cross hair line.
8.Stop motor if running and let star drift.
9. Align the path of star to one of the cross hair line of reticle by turning reticle in the holder.
10 Start motors and bring star to the centre of reticle cross hair. Let the mount track at siderial rate.
11. If the star drifts up , turn the azimuth adjusting screw so that the star moves away to right from current position.
12 . If the star drifts down, turn the azimuth adjusting screw so that the star moves to left from current position.
13 Bring back the star to centre of reticle cross hair and repeat process 11 or 12 as required. Do this till star remains

stationary for about 5 minutes. Star may move a bit horizontally, but this does not matter.

This is the easiest way I do, and it takes about 15 minutes average once you get the hang of it.

Kochu/1-6-12

[weixing]

Hi,
Or you can try the shoot and stack method... shoot lot of shot at shorter exposure time (at least 1 min each) and stack. This method do not require guiding and minimum equipment requirement, but still can get decent image... you just need more hard disk space for storing and processing all those RAW files. If you are using this method, don't need to get dual axis, single axis will do.

By the way, get the f6.3 focal reducer/flattener for your C5 is recommended.

Just my $0.02.

Have a nice day.