Set-Up by the Numbers

[rabbithutch]

Does anyone know of a web page or forum post or other online article that describes set-up steps in a 1, 2, 3 . . . fashion?

I'm very near (I hope) to buying an 8" dob. I've read enough to know about leveling the base and orienting it to a bearing and even have a passing understanding of elevation/declination. I think I can handle those things - assuming I understand how a dob mount works. Where I hit a wall is in knowing what to do next.

For example, the scope I have my eye on has a telrad and several ep's and filters. We will assume - for purposes of this question - that the scope is collimated. Assume that I have properly leveled the base, and have it oriented due South (180 deg) and have the elevation set to view something in the Southern sky and that I have a viewing objective chosen - say Orion. Where do I go from there? Did I leave anything out?

Looking at the 30 deg - 40 deg North latitude planisphere I have, Orion appears to be about 35 deg West of due South. Assuming I can eyeball it and properly identify the belt, I would rotate the base and point to belt then raise (or lower) the OTA to the correct altitude. I assume - never having seen one - that the telrad has some kind of red dot and cross hairs that superimpose over the night sky allowing me to lock in on Orion's Belt. How do I know if the telrad is properly mounted and aligned with the mirrors?

At this point, if I've done everything right, my instinct tells me that I want to look through an ep and focus the image. I have no idea, however, which ep to choose or any of the fine points wrt focusing on a moving target.

From the reading I've done, let's assume that I chose the 25mm ep. If I understand correctly, using a 25mm ep on a 1200 mm scope would give a magnification of 48X (1200 / 25 = 48). If I wanted to magnify the image, I would go to a maybe a 10mm ep. 1200 / 10 - 120X. Do I have the ep to fl ratio formula for magnification right?

Can anyone tell me if this process is anything like the reality of using a scope? Please tell me if I'm over- or under-simplifying the process. Also, I have no clue how the filters would change the viewing. A polarizing filter - if it is like using one on an SLR - will align the light rays as it's rotated. On film, this would help saturate the colors, but what effect does it have on viewing where colors are not as frequent in the ep? What about colored filters?

TIA

[brantuk]

Hi Rabbit - I can only describe my reality of stargazing lol. It sounds like you're set up ok with a levelled base. I'd just put the tube on and start pointing at anything you fancy (from stellarium). Useful to have a small list with you.

Play with the ep's to begin with and see what you like. !0mm and 25mm are fine to be going on with and the difference in views will soon reveal which way you want to go.

Dependng on the focal ratio of your scope you may eventually fancy some higher grade ep's of various length. Possibly 30-40mm for nice wide angles on large dso's, and possibly 8-20mm to fill gaps and magnify planets. Have a read of Andrews "How to choose an eye piece" thread in the Primers Section - it's really very good.

http://stargazerslounge.com/primers-tutorials/63184-primer-understanding-choosing-eyepieces.html

Other than that - just enjoy the scope and see which way it takes you - that's how I got going

[msinclairinork]

Hi,

Sounds to me like you are worrying your self a bit to much over this. It is easy done though when you have no scope to play with. Once you do get out that first night, it will all click in to place, as it really is all very simple.

Basicaly with a dob, you can just go out and point at somthing and view it...simple as that!

Yes it is best to level the scope first, then find the object to view, and usualy the best thing to do is start with a low power EP such as a 30mm? just so you can line up the object easily, then you can start bumping up the magnification, and it will all depend on what the conditions of the sky are like to what mag you can get up to with out image degregation.

The Telrad IMO is the best finder, Line it up on somthing as far away as you can see during the day..like a church spire or telegraph pole.

I use these free Telrad finder charts to help me locate objects Index of /deepsky/messier/charts

just download them and print them out as necessary or make a small booklet. You will see the concentric circular rings..this is what the telrad is all about. It just gives you a better sense of scale than just a single dot. Also the free planetarium softwear Stellarium has a plugin in the settings section to show a scaled telrad which is really helpfull. As you can find a way to your object buy 'star hopping'.

As for filters check out http://stargazerslounge.com/primers-tutorials/84192-primer-understanding-choosing-filters-visual-use.html

So basicaly just get out there and set it up as you mentioned. Point the telrad at you object and pop your lowest power EP focus it and do any fine adjustments to center the object then start upping the power and focusing as you go. Really is as simple as that

Good luck and let us know how you get on,

Hope that helps,

Michael

[John]

I agree with the others - the dob design is simplicity itself - just put it down on reasonably level ground, point it at something, and observe. Give the scope 30 mins or so to cool if it's come from inside and you can check that the Telrad points where the scope is pointing in daylight buy using a distant object like a telegraph pole or a chimney - it needs to be a mile or so away.

The Telrad projects 3 circles, like a target. You adjust it's alignment with the scope using 3 small white plastic nuts on the flat face below the view screen.

[pvaz]

A dob is almost as easy as using binos. You point and you look.

Sometimes pointing it the tricky part but you get the hang of it with practice.

[valleyman]

Dobs are so easy to use, just point and look. I agree with everything already said.

I fitted some kitchen unit feet to mine to adjust the level (10 minute job)

Also if yo get a Wixey from FLO.(magnetic angle gauge) all you need to do is point he tube in the general direction, set the Dec with the Wixey using Stellerium for the coordinates and just drift the tube in RA left or right and you will find the target using a 30/40 ep.

[rabbithutch]

Thank you, all, for the responses.

The anticipation is building up in me as if I were a kid again. At 69 not many things do that so easily.

I have bookmarked the Messier charts and will print them out as I begin finding them. Those charts will be most helpful.

I've read the article on filters once. I'll have to read it again and maybe a third time before I claim an understanding. The piece is very well written. The multiple reads are a function of an aging brain, I'm afraid.

I'll look into the Wixey. I've seen that brand and several others offered by machinists' suppliers. My main concern is batteries. I've read that some use a camera or watch type battery and that the gauge draws on it constantly whereas others use AA type batteries and only draw when in use. Is this valid information or inter web rumor?

Again, thank you all for the responses.

[brantuk]

Sounds like rumour though I may be wrong - mine has the watch type battery and can be switched off - it allways seem to work when switched on again without undue drain

[valleyman]

Mine too Bran, never seems to go flat

[JamesM]

Hi Rabbit!

Congratulations on nailing a scope at last (I have been looking for you in the texas region!) I hope you go for it cos I know you've been waiting some time.

Best of luck with it and let me know how you get on! (I'm almost as excited as you)

James