Orion Deep Space Explorer 8" Newt

[rabbithutch]

Several months back, I purchased a used Orion 8" Newtonian reflector on a Dobsonian mount. This scope is pretty old - I was told it dates to the early '90s. Because I bought it here in Texas and because the literature indicates a California address, I believe this is a US Orion (I've seen distinctions made between US and UK or international versions of this scope), but I don't know where it was made. The secondary mirror is attached with a single vane.

At some point, I'm going to have to clean the mirrors. Looking into the tube one sees various bits of dust, etc on the primary. I know that everyone cautions about not cleaning mirrors, but I think accumulation of crud over its age means that the time has come to give it a bath. I will check here and read as many web articles as I can before doing so.

Because the cleaning will entail removing the primary from the ota, I'm certain to learn new and important things about telescope construction and their care and keeping. For example, I've only read various descriptions of the screws and bolts that position and hold the primary mirror. I doubt that all scopes are alike in this respect and believe that age might make this one a bit different. At any rate I thought that the event might be a good inducement to take advantage of any improvements that Bob's Knobs might make. Viewing BK's web site does not reveal a Newtonian by Orion with the appellation "Deep Space Explorer."

While I'm certain that I could sort out any issues with Bob, him of the knobs, I thought I would first ask here for any information one might give me about my old scope. I would be interested in any information about its use and care, its capabilities and limits, suggested improvements (eg, should I consider a 4 vane secondary mirror upgrade? . . . is it even feasible to consider?), etc. I have a Telrad (awesome) and various EPs which, for now, are serving my needs. I would like a better focusing mechanism (it lacks a Crayford type).

My goal is to optimize the value to be gained from my current investment but want to avoid gilding the lily by too much tinkering.

TIA for any information.

[A McEwan]

Hi bob.

I remember reading in a comparison review in Sky & Telescope back in the olden days, that the Orion Deep Space Explorer is very similar to the Celestron Starhopper and the Meade model of similar size that was available back at that time. I believe one difference was the different mirror cells used and that fact that one or other of them didn't have a solid plate behind the cell, which meant faster cool-down time. I forget which model it was precisely.

Anyway, the point is that there are many 8" f5 or f6 Dobs out there that have very similar workings and mechanicals in their makeup. It may not be necessary to dissassemble the entire mirror cell to remove the mirror. In many cases the entire cell slips out of the back end of the tube after undoing half a dozen screws. The mirror is then held held in position in he cell by means of three clips that sit over the very edge of the mirror, and which are removed by undoing holding screws. The mirror then plops out (carefully) for cleaning and is reinserted in the same way. Don't do the clip screws up too tight though - in fact not even to finger-tightness, as that can cause pinched optics .

Not all Dobs have this fitting method. Sometimes the primary is held against the cell by means of dabs of adhesive. Sometimes be pressure against the edge of the mirror.

Personally, I don't like single stalk secondary supports. The diffraction pattern produced is a single straight line, passing through the target object and reaching across the field of view. I would rather have a 4-vane (thin) than a single stalk any way. I would similarly avoid 3-vane stalks, as their pattern is even uglier (to my eyes)!

Although I don't have any experience of Bob's Knobs, I would expect any that work for brand A 8" Dob to also work for brand x, y, and even z 8" Dobs. I may be wrong and if so I hope someone will correct me. Again, personally, my own 8" f6 GSO holds collimation for years at a time with only the standard springs in place and I feel no need to replace them.

You may at some point want to invest in a better focuser though, and there are plenty of options, from 2" Crayfords, dual-speed Crayfords, standard rack & pinions, motorised Moonlites, etc. I found my first good focuser upgrade on the standard 2" rack & pinion on my Dob was to add a Skywatcher Autofoucser electric focus motor with hand control. It might not fit the focuser you have, though, depending on the model.

Do you have any pics of the telescope?

Globs will be nice in that scope, as will the planets with plenty of good detail on the gas giants. The Moon will rock you. Open clusters will be excellent too. Galaxies will merely tease you though, letting you know that they exist without really letting you resolve significant detail - apart from the brighter Messier ons anyway. A dark sky site will be a good accessory to own with this scope.

Ant

[rabbithutch]

Thank you, Ant!

That is great information to know. I know that 8" newts on dob mounts are plentiful. I was uncertain by how much their bits and pieces are similar or dissimilar.

Can you identify or recommend sources for upgrade components (focuser, 4 vane secondary mirror mount). I think an improved focuser will be first on my list with the secondary support vanes second.

Again, thanks for the great information.