balancing confusion

[Scott]

i've seen on youtube and been told by people that you should balance your scope on 3 axis. i understand the need to balance the tube to the weights and the tube itself but i can't for the life of me understand balancing the tube vertically. i turn the tube until it's balanced vertically but as soon as i use the scope for viewing i have to spin the ota so surely this just nullifies the vertical balancing i've just done. am i missing something here?

can anyone clear this up for me? i do perform all 3 balances but i just can't understand why.

sorry to be a pain...

[JamesM]

Hi auspom, it does seem quite confusing. Have a look at

video in which the guy tackles this very question and the reasoning behind it (at around 7:15 onwards). This series of videos are pretty good and certainly worth watching.

James

(p.s hope its not the one you have already seen!)

[marshy123]

That is a superb balancing tutorial, thanks for the link JBM.

[Scott]

thanks James. i'll certainly have a look.

[Scott]

i've watched that video james. i've probably not explained myself properly in the op. i know how its done but my question is... once its balanced vertically and i decide to view something i'll usaully have to rotate the ota which then just puts the vertical balance out again. is that right or wrong? i just can't get my head around that bit.

i can see this working on an alt/azimuth mount where the tube probably doesn't have to be rotated after balancing but not an eq mount. (unless i'm doing things wrong) for instance when a meridian flip is performed the focuser is in a completely different position.

[JamesM]

I understand now what you mean now and agree with what your saying. In fact, this balance can also be affected by using different sizes of eyepiece (1.25" to 2") which can vary hugely in their weight and again contribute to an imbalance. Did you notice that although he mentioned about eyepieces, he didn't have one in when he was balancing? To be honest the video is showing you the principles which is fair enough but in reality, I don't believe it makes a great deal of difference for those of us who are using the scope to observe with. Where it certainly does make a difference is when you are imaging (he does a lot of imaging tutorials too) where this level of balancing precision is required so as not to affect the tracking accuracy. In that situation, all the gear will be attached right from the start (... not changing eyepieces) and there won't be a need to rotate the scope for a more comfortable viewing position because you are using a camera to record the view.

As good as all these mounts are (HEQ5 & NEQ6) they are still built to a price and contain inherent inaccuracies which are within acceptable tolerances for the purposes that were intended. The same can be seen when polar aligning with these scopes, as they only record 30 days for each month, completely ignoring February, with hours divided into 10 minute segments etc. We all endeavour to get it as good as is realistically possible (fettling and men in their sheds:D) which is part of the fun really and is usually sufficient for most of our needs. So I wouldn't worry to much but you were certainly correct to question the logic of its inclusion!

Clear skies

James

[Scott]

hey James, thanks for taking the time to help me with my question. i'm just glad that i'm not missing something obvious that may have been putting unnecessary strain on my mount. i love your comment about men in their sheds. to be honest it's a part of astronomy i really enjoy, being presented with a problem and trying to sort ot out without spending a kings ransom. pulling webcams apart (don't think there's any left in our house that haven't been pulled to pieces in my quest for a cheap webcam for my very amatuer a.p. still, it gives us something to do on these rainy days/nights. next project.. bahtinov mask.

[ollypenrice]

In visual use that kind of fine balance isn't necessary. It's for imaging that you try to get the three axes right.

Olly

[Scott]

cheers olly

scott

[JamesM]

Glad that's sorted out for you and was no trouble at all. Making your own Batinov mask is certainly something to get stuck into on a rainy afternoon and to help you along, you might want to take a look at this as a means of getting the size right.

Clear skies and best of luck!

James

[Scott]

thanks for the link james, its actually the one i used to generate my template but i think i'll give it a good read before i start cutting the perspex im going to use.

[JamesM]

Out of interest, I wonder why you are using perspex? When I did mine, I used some inexpensive 3mm black foam, easy to cut and comes in a variety of different sized sheets which you can easily find in most craft and hobby shops.

Clear skies

James

[Scott]

just because i had some lying about. figured it'd last longer than cardboard although the foam would be a easier option. not likely to break either.