Ok you Dob people....

Declan --

Transparency (ie: fog) doesn't matter for collimation; seeing (the stability of the atmosphere) does.

Most of the time (but not always), fog indicates good seeing, and so is good for collimation. I wasn't out last night, but two nights ago had 7/10 seeing in Louth, which is pretty decent (I've seen 8/10 in Ireland, but never better).

As for not breathing on your eyepieces: it takes practice. (More practice, evidently, than a couple of years of observing as I'm still doing it. )

Cheers,
-- Jeff.

thanks for that jeyjey. now not only will I have to get a patch to wear on my left eye while observing...I will have to get one for my
mouth as well :x

anyway steamed up eyepieces, fog, ignorance,fear and the late hour ....I thought leave till next time.

declan

Declan --

One thing I forgot to mention -- just fanning the eyepiece with your hand will usually clear it in a minute or so. The other thing that can help is to lower the eyeguard -- it makes it harder to position your head when you can't rest your eyebrow or cheek on the eyeguard, but the extra air movement can delay fogging (at least eyeball fogging, if perhaps not exhaled breath fogging).

Cheers,
-- Jeff.

OK as a complete novice to the subject of collimation, (only purchased 10" starhopper last week) I did astar test using polaris last night but the seeing was a bit misty! crystal clear views of the moon and that was pushing magnification to 160x (15mm and barlow2) around 8.30ish saturn was still down in the murk but when i did image it - i could clearly see the division between the planet and the rings but not much colour varience on the surface.

Question: is the last 2 nights less than ideal to collimate a scope due to moisture in the air?


declan

I had a look at the moon last night too with my dob. The seeing was the best in ages. Its usually like looking at the moon at the bottom of a pond at high magnification. Last night though my views were pin sharp with my 8mm at 187x and 5mm at 300x. While not pin sharp the views I had with my 3.5mm at 428x were still pretty darn sharp and my best view yet. I even 2x barlowed the 3.5mm for 856x !!! and I was still getting very pleasant views!

As for Saturn, I didn't have a look last night but generally I don't see any colour variance ever. I can usually see the gap between the planet and the rings and the shadow of the rings on the planet. On decent nights I can see a faint cloud band above the ring. Only once have I seen the Cassini division at the edge of the rings (at the ansea). Its always white for me though. No hint of colour to my eyes.

We might actually have a better chance of seeing the cassini division in a month or two. Although the general trend is that the rings are closing up at the moment till they are edge on and invisible in 2009, they will actually open back up a bit in about a month or so for about a month before they resume their thinning. All to do with our position in our orbit in relation to saturn.

As for collimation. Star collimation is generally for fine tuning your collimation, not for doing it from scratch. In other words you would use your collimation tools to get your scope 99% there and then star test to get it that last 1%. Seeing is rarely good enough though so in general you just have to make do with 99%

As we are talking about dobs - just a quick note - and i know it should be on observing equipment side. I purchased a little triangular trolley with 3 4" wheels in Lidl's last week - brill for moving your dob about.




"Rather have a full bottle in front of me, than a full frontal Lobotomy"