where av i gone wrong....

[garethmob]

heres a pic i took the other night

it was at 135mm ∞ focus 30 pics at 10s each tracked but not guided

stopped down to 4

now one thing i made a mistake on it is at iso 200 (i must av accidently changed it in the dark from 800)

im really really rubbish with photoshop so its just had the DSS processing done

ironically it is the best pic iv taken but any advice on improving it or any future i notice some pics appear to be vinegretting in the lower left and right of the pic :S where the middle seems more pinpointed *confused*

thanks guys

[JoLo]

The vignetting and out of focus off axis stars may be due to the lens you are using...what do you use? Higher quality lenses will have flatter fields and reduce these problems. There is also software that can help with these issues, both can be done in Photoshop as well.

When using a lens on a tripod or piggyback, i never stop it down more than two stops. For instance, I have the f/1.4 50mm Canon lens that I always shoot at f/2.2 (two stops). This give me the advantage of getting the pinpoint stars and having the advantage of a fast lens.

I find I can generally go about 25 seconds max before i get trails (near the pole, much less near the equator), but that is at 20 or 50mm...at 130mm, you can already seeing your stars start to bloat from trailing. Once you get above 80 or so mm, your exposure time shortens quickly when not tracking the object.

I would also check the focus. Some of my lenses focus right at inifinity, some do not. The only way to know, is to take test shots and vary the focus off infinity in both directions....mark your point of critical focus for each lens. Do you have live view? Incredibly helpful when it comes to focus.... Also, when checking focus, zoom way in and check your stars...they should be no bigger than the focus marker when zoomed in max.

Check your focus, do a minimal stop down on aperature, and check that ISO....determine what combination is best for your location and amount of light pollution. I think your image looks great...tweak these few things and you are on your way!

Joe

[Stephen]

Check this site out for max exposure times - ScenePlanner - Tools for camera users - Astrophotography Exposure Calculator

[garethmob]

it was a 135mm tamran m42 pantex lens, so a fairly old one, but i thought the tamron len's were good?

the lens is a F2.8 so F4 was only one step

sadly i dont have live view as its a canon 300D

what do you mean focus at both ends, (twist it all the way one way an all the way the other?)

thanks for the advice joe i did mess up with the iso usally 400-800 depending on where i am in the garden suits better though... but iv swapped it now

[garethmob]

thanks for the site kh3ldar my lens isnt there but closest shows 7s which with the bloating joe mentioned would make sence one thing im looking forward to though, i can take lots of pics n my battery wont go flat!

[todd8137]

i did cygnus a while ago unguided at 800iso 30secs subs flats darks ect i got about 35 mins worth but forgot to clip the filter behind the lense which gave me horrible orange glow heres the link to the post am sure with more time you to will crack the darkside

http://stargazerslounge.com/blogs/todd8137/815-start-my-mega-wide-field-shot.html

never give up its a pain but it keeps me going out till i hit the money shot i constantly save and add subs to this set of pics

pat

ps great first attempt

[JoLo]

With my lenses, I check focus on both sides of the infinity mark with test shots. Some of my lenses (usually Canon) focus right on the mark, others may have best focus on either side of the mark...just try test shots with your lens on the mark, just above and just below. If you see focus improving in one direction, continue to move the focus in that direction and take another shot....you will be able to tell when you have hit the mark. Move the focus off the mark in very small increments.

I have a 20mm Tamron lens, it is my favorite...very sharp when stopped down, nice wide angle even on the 450D with a 1.6 crop factor. The focus, however, is actually beyond the infinity mark with this particular lens.