Polar Alignment For Lunar Photography

Hello All

Just started to astronomy and decided to dive right in by trying to take a few pics of the moon using my 400D and SkyWatcher 6" reflector.

I tried to polar align my equitorial mount (EM10) and it seems to work while viewing the likes of Saturn, keeping it perfectly centered for a prolonged period, however when I look at the moon at high magnifications it does not fix to the same location.

I know the moon revolves around the earth which explains this (saturn taking a lot longer to rotate around the sun), but is there any way of tracking the mooon with an equitorial mount so that it will stay fixed to the telescope.

I ask this because by the time I have set up my camera and am ready to take the picture, the moon is out of the field of view!

Here are a few images I managed to take which I don't think are too bad considering I don't have a clue what I am doing!

s86.photobucket.com/albums/k83/danielsen...onal/Astronomy/Moon/

Any recomendations on books that would define exposure times/iso levels etc or would you say experimentation would be the best bet?

Sorry if this is a bit simple! But i was thought there is no such thing as a stupid question (although i have been proved wrong quite a few times in the past!)

Thanks for any help, a clueless techie gazing to the stars awaiting your advice!

I know the moon revolves around the earth which explains this (saturn taking a lot longer to rotate around the sun), but is there any way of tracking the mooon with an equitorial mount so that it will stay fixed to the telescope.

I believe advanced equatorial mounts (not like those of the ETX series) have a different slew rate for Moon tracking. But I don't have any more info on that.

Welcome to the boards by the way!

Seanie.

Daniel, I know Celestron has a option for tracking the moon, but give Carl O'Beirnes a call or pm him for his number. He would be happy to help you out or even show you. He only lives up the road in Balbriggan

Thanks Seanie and Gary for the prompt replies.

My EM10, besides not having different slew rates on the N/S polar alignments is otherwise a fine sturdy mount for me! (has got different slew rates for the electronic manual ra/dec controls though so might play around with these, although as far as i can remember the moon moved in both).

I will play around with it and see if i can manage to find out something. If that doesn't work I will focus on photographing things that aren't moving at vastly different rates in the sky!.

I just bought a etx-70at, so might try lunar photography on that since it can track the moon (just liked the idea of something that could fit in a backpack!).

Anyway, thanks guys... good cristening into the boards!

Daniel,

You should not need a special rate for lunar photography. The moon in its orbit only moves about it's own diameter every hour so with the short exposures needed for this type of photography the difference between the earths rotation (sidereakl rate) and the moons apparent motion (lunar rate) would be imperceptable. If the Moon is moving faster than its own diameter every hour then you need to look at your mount. It could be that your general polar alignment is off the mark.

To cut to your point about the Moon moving while you setup your camera gear. Your gear should be setup on the scope before you even begin to focus on the Moon. i.e Attach camera->Centre Moon-> focus -> Centre Moon again if necessary->Shoot. By adding the extra weight of the camera to the scope you may well be causing the scope to move itself.

As for exposure times, you're right suck it and see. Generally keep the ISO low ISO 0200 should be fine for a bright target like the moon. Start whith a short exposure and keep upping it until the moon is too bright. Somewhere inbetween will be the correct one or two. No harm having too many shots!

Thanks Dave, for your reply.

I am sure you are right, my polar alignment was probably off, will make sure to do a 2 star alignment next time and track a star for a little while to make sure it is correct.

The telescope was pritty much horizontal and I then attached my camera and other stuff, so that would have probably shifted the telescope a bit (never re-adjusted my counterweight as well, which I'm sure did not help)!

Think I might pull the reins on the photography and get a grip of the basics (2 star polar alignment, setting circles, constellation names etc...) before I end up hanging myself!