Any rules for drift alignment for equatorial regions?

[starfinder]

I recently got an LXD75 from Astrobargains. For the first time since I bought it in around 1998, my C-5 has been mounted on a goto mount. It has finally entered the 21st century.

I am starting to do some limited DSO astrophotography with a WO80mm. I have been forwarned though about the dangers of dabbling in that slippery slope by some seasoned strictly visual observers. I know I know, but still...

Anyway, my main interest I think will still be wide-field constellation photography of the sort done by Akira Fujii and Bill/Sally Fletcher, like this:
http://www.scienceandart.com/photogemini.htm


I have done rough polar alignment by setting the mount to point about 1.3 degrees up using a bubble level and pointing it North with a compass and cross-referenced with Google Earth imagery of distant buildings.

Next, I have been trying out drift alignment and been reading on the web about declination drift alignment, such as at these sites:
http://www.petesastrophotography.com/
http://www.astro-tom.com/tips_and_advic ... gnment.htm


My question is, for our equatorial region which is neither much north or south, are there any special methods or rules for drift alignment?

For example, do we also ignore RA drift and only look at declination drift which those websites say should be done?

Also, those websites state that for checking errors in the mount's azimuth (east-west, left-right) pointing, the selected star should be near the intersection of one's meridian and celestial equator. This means for us selecting a star nearly 90 degrees overhead, which seems quite impractical.

Hmmm... any tips or rules of thumb for our equatorial setting? Thanks!

Poor us, the polar scope is completely useless. That concept must be very alien for our cousins up north and down under. For them, using a compass must be heresy too!

[MooEy]

yes yes, u ignore ra drift, infact, for most gd mounts u wun have much ra drift, china mount on the other hands have pretty wonderful ra drift that throws most beginners off. If u notice the star wriggles back and fro in ra, it's time to do some adjustment to the worm/wormgear/ra axis, if it does't help, move on, vixen mounts are dirt cheap and does a wonderful job.

no no, for us, we follow north, mount points north, follow procedures for north.

yes yes, u point at a star practically at ur zenith to do ur azimuth adjustment first. adjust ur diagonal to be inline with ur declination. rotate ur reticle eyepiece of match the direction of the star drifting inside the eyepiece. identify which side is north and which side is south. ignore all east/west(RA) drift.

next u pick a star near the horizon and equator at either east side or west side. pretty much the same steps applies.

~MooEy~

[weixing]

Hi,
Drift alignment is more accurate than polar scope and are the prefer method use for doing long exposure astrophotography. The method is basically the same... only the interpretation of the result and action is different. See this article on Sky and Telescope: http://www.skyandtelescope.com/howto/diy/3304261.html

Also, those websites state that for checking errors in the mount's azimuth (east-west, left-right) pointing, the selected star should be near the intersection of one's meridian and celestial equator. This means for us selecting a star nearly 90 degrees overhead, which seems quite impractical.

Err... What do you mean impractical?? It's overhead and EQ mount can point overhead easily without a problem... unless you are trying to do drift alignment indoor.

Have a nice day.

[starfinder]

Hey tks for the replies!

Well, I did think that there might be different rules or at least some special methods since we are at the equator.

Ya, I need to do alignment indoors since I am trying to image through my east-facing window and south-facing balcony. If a star must be selected near the zenith for the azimuth adjustment, that would be impossible. Hmmm.... Perhaps at 60 degrees up the drift would still show, only much more slowly.

I wonder if anyone has used different rules for the azimuth adjustment to good effect.

I think the motto for astrophotography might be:
"Not the triumph but the struggle."
or:
"Its 90% perspiration, 10% results."

Ha...

[VinSnr]

Hey tks for the replies!

Well, I did think that there might be different rules or at least some special methods since we are at the equator.

Ya, I need to do alignment indoors since I am trying to image through my east-facing window and south-facing balcony. If a star must be selected near the zenith for the azimuth adjustment, that would be impossible. Hmmm.... Perhaps at 60 degrees up the drift would still show, only much more slowly.

I wonder if anyone has used different rules for the azimuth adjustment to good effect.

I think the motto for astrophotography might be:
"Not the triumph but the struggle."
or:
"Its 90% perspiration, 10% results."

Ha...

More like 90% are wasted shots, only 10% shots are useful.

That's life for a AP guy.

[weixing]

Hi,

Ya, I need to do alignment indoors since I am trying to image through my east-facing window and south-facing balcony. If a star must be selected near the zenith for the azimuth adjustment, that would be impossible. Hmmm.... Perhaps at 60 degrees up the drift would still show, only much more slowly.

I think should be able to do it if you use a star as high as possible, but might take a long time. Remus should be able to give you more advice as he is the expert in indoor Astrophotography... ha ha ha Anyway, if your exposure is not long, just use compass to align as accurate as possible and use the drift alignment to correct the polar axis altitude. Then use your GOTO to correct the rest of the error loh. I don't think field rotation will appear for short exposure.

More like 90% are wasted shots, only 10% shots are useful.

More like few hundred MBs per picture. Running out of hard disk space very fast.

Good luck and have a nice day.

[zamri]

Hahaha. Remind me last nite. After the hard pain setup my scope ready, then here come the cloud cover the stars .
Waited almost an hour then left it covered at my balcony thought I can proceed later on about 1 am. But there's it, felt asleep all the way till morning.

[rcj]

hoot! guys, you're doing well with the explanations already....let me seat back and eat popcorn.... ;P