Posts Made By: Lorne Johnson

I don't think you'll go wrong with either of those eyepieces.

john altenbach said:

Just got an ad email from a dob scope builder about a price increase soon for all mirrors:
"Corning is closing their Pyrex factory this Fall. There will be no more
Pyrex mirror blanks. Alternate suppliers of borosilicate glass (Pyrex)
charge alot more. Expect considerable price increases in the future."
Has anyone heard more about Corning stopping production of their pyrex mirror blanks? If so, this would probably affect most telescope prices.
John

Since I am working on a medium size dob project, I decided to move ahead more quickly, and placed my order for a 12.5 inch. Naturally I asked about the situation, and this is what I was told.

Corning is shutting down their plant, and there will likely be disruption of the supply of mirror blanks. However, Corning has already moved its production of pyrex to Ireland due to environmental complaints from Canada about acid rain. The production in Ireland is being sold off to an overseas concern. The situation will almost certainly settle down over time, and pyrex is unlikely to dissappear.

I would add, that energy costs and plenty of other factors could well result in significant price increases as a result.

You give a good description of the kind of atmospheric turbulence that we have been seeing of late in my part of the country, New England. So it is pretty likely that is at least a part of what you are seeing, quite possibly all of it. (So I wouldn't despair.) But, physiological factors may also be some part of it.

It would be pretty hard to improve on Jon Isaacs' advice, so I won't try. I will note that he indicates the mount as the weak point on many of the scopes you were considering. I don't think that you would go wrong with a 6" f 8 dob, and the dob mounts are really very stable.

I would also agree with Joanne Smith that the 8" f6 dob works well and is comfortable viewing from a seated position. That would be my choice for the best all around scope (about the same size and weight as a 6" f8, and exactly the same focal length). It does not quite fit your $250 budget however.

I would seriously consider a Siebert 34 or 36 mm observatory eyepiece. I find mine to be more usable than the 35 panoptic.

This depends on what you mean by,"the whole veil." The veil has two separate brighter sections, with dimmer areas in between. In my 8" f 5.7 (which is f6 for practical purposes), the larger section on the veil will not fit into a 22m panoptic, which is just over 1.2 degrees int that scope. For about $75 dollars the larger section of the veil will look very good in a B&W 300mm 80 degree eyepice, but the stars in the outer 35% (or more) of the field won't. In either the Siebert 34mm or 36 mm (what i use) observatory grade ($200 new, sometimes seen used for about $150), the veil will look great, and the stars will be much better. You can also get the separate section and the dimmer nebulosity in one view, under very dark skies.

I can get both in the Siebert with my 80 mm, but I confess that the two views in the 8" are in a different league.

Good luck,
lorne Johnson

[QUOTE]Lee Spain said:

While I'm waiting for my big telescope to come, I'm keeping busy with little projects. As you know, there is nothing more dangerous than a beginner with a box of objective lenses from the Surplus Shed. Here's my really basic question.

If a refractor objective has a focal length of say 350mm, does that mean that the length from the objective to the mirror in the diagonal us 350mm? Or is the total length from the objective to the eyepiece supposed to be 350mm?
And how does this measurement relate to the focal lengths of my eyepieces? I've had troubles where I get something set up just fine for 25mm eyepiece, but I have to totally readjust for a 10mm eyepiece. Thanks!


The focal length is measured from the objective lens to the eyepiece. Eyepieces have their own focal point depending on design, hence your having to refocus when using different eyepieces. I you find that you often use one eypiece that is quite different from your other, you may be able to solve the problem with a "parfocal ring" which simply keeps the eyepiece from inserting fully into the diagon alley.

Jim Nelson said:

I'm not sure if the "Beginner's Forum" is the best place for this or not, but here goes:

There's a question I regularly see asked of beginners looking to buy their first scope. It's some variation of this:

"What kind of observing do you want to do?"
or
"What are you most interested in?"

Now, the question has merit. I see where it's coming from.

But who among us, as beginners, had well-informed and decisive ideas about what kind of observing we would like best, BEFORE we've put in observing time? Even if we've looked through a few scopes a few times?

Most of the time I see this question asked, I'm pretty sure some newbie on the other end of the internet is sitting there with a deer-in-headlights look in their eyes.

While we should ask Who is using the scope (how old? especially), and Where they'll be using it (at home in the country; local park; city balcony?), shouldn't we assume that any newbie should be getting a good all-around scope, instead of something specialized for a type of viewing that they may well change their minds about after a few times under the stars?

Jim, you are, of course, correct.

However, I think that the question is essentially rhetorical, meaning, "What the best scope, mount, eyepiece, or locationis depends upon the specicifics of different kinds of observing."

The best answer that we tend to give is, "Go to star parties and find out what interests you before you start shelling out a lot of money, or even a little money." This could be argued to be similar to the quotation above.

My comments are not meant as dissagreement.

Lorne Johnson

Casey Whalen said:

After just receiving my Skyquest xt6 (dob), i'm pretty happy with it but i'd like to be able to get the most out of my new scope. I'm looking at adding to my eyepiece collection, my xt6 came with 2 eyepieces (both 1.25") 25mm and 10mm pieces. I'd realy like to be able to see some deep space objects..sounds like my xt6 is somewhat limited (to 6 mag stars at the most?) but what about messier objects. I guess my question is what eyepieces should I invest in? From what I understand a lower MM is good for planetary viewing and a higher MM is good for deep space. Can someone point me in the right direction here? Funny how after I get my scope I have a lot more questions than before I had it, hehe.

You should wind up with a lot of advice here, most of probably quite good. I'm assuming that the Sky Quest is f/8 and 1200 mm focal length, and the 25 mm is a plossl. At 48x and a 1 degree true field of view, that eyepiece is great for looking at Messier Objects. Given time and exoerience, you should be able to identify all 109 of the Messier objects with it. With that 1 degree field of view, finding them may be quite a bit harder.

Assuming that the scope has a 2 inch focuser something like the B&W 300 mm 80 degree eyepiece for less than $100 (maybe $60 used) would be a very good finding eyepiece, there are also GSO's and Proximas that should be very serviceable at f8. I use a 36 mm Siebert ($200) which holds up much better at shorter focal ratios, but it costs more too. Any of these will give about 2 degree field, which is very helpful for a beginner, and provides spectacular views of extended objects for anyone.

If your scope has 1.25 inch focuser, then a 32 mm plossl will give you as much true field as you are going to get, and is the obvious choice. This should give you excellent image quality across the entire field.

Best wishes
Lorne Johnson

I think that this is a fine idea Floyd. But, I doubt that it will stop all of the complaining. Perhaps some will simplky resort to complaining about the form. (Which is different from making thoughtful suggestions.)