New Orion SkyQuest XT8 Dobsonian

[cap603]

I received the scope on June 1st and assembled it today, June 3. It took about an hour and a half, with no complications. It may not be perfectly collimated, but being a novice I'm not in a hurry to start moving things around. The leaves on a tree about 1/4 mile away seemed clear enough.

Of course, I wanted to try it out tonight, but there's a thin overcast. Acturus, Spica, Saturn, Mars and Regulus are visible through the haze, but at 10 PM local, that was about it. I can barely see Ursa Major. To avoid frustration and disappointment, I decided to wait for "first light."

One question for you veterans, however. When I was looking through the collimation eyepiece, I noticed specks of what I assume is dust at the 1 o'clock position of the secondary mirror (I think). This evening I was inspecting the main mirror with a red light and noticed what appears to me a good number of flecks of dust all over it. These weren't visible without a very bright flashlight (torch). While acknowledging nothing is perfect, I am rather fussy after having spent so much coin. Is this dust issue something to be concerned with or should I just let it go?

Thanks in advance.

[pvaz]

You should leave it alone as it won't affect the image. They just reduce the amount of light gathered by a tiny fraction. Eventually in time you'll want to clean but thats a delicate work you should leave for later.

You may want to check the dust cover. I have the orion XT8i and the dust cover scratched the inside paint job and covered my primary with the scraps. The 2 scopes have some differences but this may well be the cause. Aside that minor design flaw, it's an excellent scope.

I broke the clips on my dust cover. Now I fit it on and then I put a home made cloth with rubbers (or whatever they are called in English) over it to secure it in place, as it haves no clips now.

[brantuk]

Was this a brand new or second hand purchase? If it was a s/h purchase then it may have been out in the field without a cover during the volcano ash incident a week or two ago.

[dweller25]

Your mirrors will slowly get dirty - don't worry about it.

Shining a flashlight at a mirror will always show dust but it has no effect on the image.

After three or four years of regular use you may want to give it a wash which is easily done without damaging the coatings if you carefully follow the many guides on the internet.

But for now it's fine - enjoy your scope and don't try to fix what aint broke !!!

[cap603]

Many thanks for the input. The scope was bought new in the US, so no volcanic ash issues. I'll just leave it alone for now.

[pvaz]

If it is the dust cap scratching the paint then you should use a cloth between the cap and the tube, or else you'll have more and more paint particles dropping into the primary.

Look inside the tube, on the top and see if you can spot scratches.

[cap603]

I examined the inside top ridge of the 'scope where the cover attaches. No chipped paint visible. I may still modify the cover based on your experience. I guess it's just plain old dust. Hoping for clear skies soon! I'd like Mars to be my first target since I reside near Mars, Pennsylvania.

[pvaz]

If the cap fits OK, then let it be. I may well have caught a faulty cap or something. No point fixing something that doesn't need fixing.

[dweller25]

Hello Jim and welcome to SGL.

I'm afraid mars is now a very long way past closest approach which way in January. If you do want to see it then try to find it in the evening twilight for the best view. You may just make out a slightly brighter Ice cap and some very subtle markings on the surface - just. Mars put on a great show this year but sadly you will have to wait until march 2012 for the next visit.

To see what your scope is capable of look at my drawings in the "Images - sketches and unconventional" section, some were done with an 8" reflector.

Saturn is a better object at the moment, it's rings are edge on. It's in the southern sky at twilight.

You have made a very good choice with your scope.

Clear skies.

[cap603]

Thanks to all for the advice. I'd like to ask about eyepieces for the 'scope. I read "Warthogs" excellent advice about selecting eyepieces. As he cautioned, I don't want to go crazy buying things, especially things I don't need or won't use.

My Orion 8" Dob is 203mm, 1200 FL, f/5.9. It came with a 25mm Plossl which provides 48x, which I think should be the "low" power end. I'd like to get one more higher power eyepiece before I head north to the dark skies of Canada in about two weeks. According to what I read in Warthogs piece, a 10mm would provide 120x; 7.5 = 160x; 6.3mm = 190x. As they say, "how high should I go?"

I don't see a need for a Barlow at this point, but I'll listen to all comers.

I also plan to get a variable mood filter before I depart.

Thanks from across the pond.

[cap603]

Dweller: I took a look at your sketches. Very impressive. Must be nice to have talent! I will be thrilled if I can even get close to seeing what you can.

[dweller25]

Jim, thanks for the kind words, I'm not the greatest artist but I do enjoy it.

When selecting high power eyepieces for a dob look for the wide angle ones, this gives you longer to look at an object as it goes through the field of view. You can comfortably go to x200 with your scope = 6mm.

[cap603]

Dweller25: Good advice again. Thanks. Orion USA offers the eyepiece described below for US$ 75.00. 66 deg field of view. Is that in line with what you advised? I wouldn't want to spend more than this. Jim

Orion Expanse Telescope Eyepieces

This 6mm eyepiece offers a wide field of view and superior optical performance at a bargain price

Great eye relief so eyeglass wearers can view the entire field without removing their glasses

Delivers sharp images with good color correction and contrast

Aluminum barrel is internally blackened to eliminate internal light scattering

One-year limited warranty

With its 66° apparent field of view, this 6mm Orion Expanse Telescope Eyepiece will definitely turn up the Wow! factor in your deep-sky observing experiences! Imagine taking in objects like the Andromeda Galaxy, the Double Cluster, or the star clouds in Sagittarius in one sweep! With an Expanse in your focuser, you can!

Expanse oculars have big eye lenses and great eye relief (13mm to 17mm). Eyeglass wearers can view the entire field without removing their glasses. All eyepiece elements are fully coated, with the outer lens multi-coated for additional light transmission. The 1.25" aluminum barrel is threaded for filters and internally blackened to eliminate internal scattering. And its fold-down rubber eyeguard enhances contrast by blocking stray light.

[dweller25]

Here's a good review ....

Head to Head: Orion Expanse vs. Siebert Optical Standards - Shootout

[cap603]

Thanks, dweller 25. There seem to be too many choices out there.

[cap603]

Dweller25: I took your advice about the cover. It snapped in a bit to firmly and I was afraid it could actually chip some paint. Instead of removing the tabs, I filled them down so the cover just fits the tube without the tabs snapping into place. It fits loosely, but that's OK. Regards

[NGC 1502]

Hi, I have an 8" F6 Dob, and a 6mm eyepiece, 200x, is good for high power on a steady night. On VERY rare nights I've gone to 240x, but I'm happy to use a barlow to get there. Quite often, 150x is as high as I need to go. Regards, Ed.

[dweller25]

Hi, I have an 8" F6 Dob, and a 6mm eyepiece, 200x, is good for high power on a steady night. On VERY rare nights I've gone to 240x, but I'm happy to use a barlow to get there. Quite often, 150x is as high as I need to go. Regards, Ed.

I have the same scope but put a computer cooling fan in the back, this also removes tube currents and the boundary layer on the mirror surface. x320 is no problem as long as the seeing is good.

[cap603]

"First light" was yesterday evening, June 7. We finally had clear skies here in Western Pennsylvania. Clouds rolled in again today and will be here all day tomorrow. As dweller 25 mentioned, Mars was too far out, though I did see it and Regulus. Saturn was quite impressive to me - and my wife (important) - although with a 25mm eyepiece i had only 48x available. Courtesy of ebay, I hope to soon have a 6.3mm and 10 mm. I had no luck looking for galaxies or clusters, but again, only 48x.

Considering all the information I've garnered here at Stargazer's Lounge, no one had mentioned dealing with neck strain. Any advice?

[dweller25]

I always sit down to observe it's much more comfortable.

x48 is ok for galaxies.

When you get chance make sure the scope is collimated.

And always make sure the scope is cooled down.

A well collimated, cooled 8" scope is a great all rounder.

[samm]

i have the same 8" dob and what i have found to work very well to keep dust out is a couple of shower caps . i put one over both ends along with the plastic cap it comes with . from the first day i had the scope i went to the dollor store and bought a pack of clear shower caps for a dollor they fit perfect over the scope ends , i hope this helps .

sam

[cap603]

Just returned from Canada and New England. Only one clear night in Canada, (Prince Edward Island). I'll try to post a photo in the "images" section.