Posts Made By: Joplin Motisher-Chittenden

Colten, I wouldn't worry too much about getting your mirror back. I would guess that the size of your mirror (16") and the fact that it probably had to be re-ground to a sphere before refiguring is what is causing the delay. I recently had Cary OWL test, retouch, and refigure a 10" F6 mirror that was originally made by Parks Optical. I should note that this mirror wasn't all that bad except for a turned edge, the surface was smooth and it measured 1/6th wave PTV. I shipped the mirror to OWL on 6/10/2008 and it arrived on 6/16/2008. The mirror was shipped back to me on 7/15/2008 and arrived back on 7/22/2008. Note that my mirror only had the figure retouched, it did not go through the more extensive refiguring process. The specs on the mirror now are 1/15 wave PTV and a strehl of .988 I haven't had any decent seeing to really test the mirror thoroughly but so far it looks good. As a point of reference a friend of mine recently sent off his mirror to be refigured after waiting 9 months in line just to send it to one of the premium mirror makers. I would suggest either emailing or calling again to find out what step of the process the mirror is in. I never had any trouble reaching someone on the phone at OWL, I usually called around 3pm PDT.

Joplin

The Vixen LVW 17mm might be worth trying, should have a feel pretty similar to the Pentax XW's (65 deg. Fov vs. 70). I haven't had the opportunity to use one myself but all the reviews I've seen about it were positive.

Joplin

Seems like you should be able to tell. Pyrex is listed at 2.23 grams/ cm3 and Plate is listed at 2.40 grams/ cm3. See this link:

http://www.udel.edu/chem/GlassShop/PhysicalProperties.htm

I'd suggest a 2" diagonal by William Optics (wouldn't worry about enhanced vs. dielectric). For low power on a slow scope I like the William Optics SWAN 40mm 2" eyepiece. It's about half the price of the highly touted 40mm TMB Paragon but the performance is basically the same in a F10 scope like yours. It would give you a nice 2 deg. field view and make it easy to find objects. An eyepiece in the 20mm range would be nice in case you decide to try for any deep sky objects. For planets I would suggest an eyepiece in the 8 to 9 mm range. Another option would be an 8-24mm zoom which would be handy for terrestrial use and would cover a good range for astronomy as well. You'll get better image quality if you stick to a 90 deg mirror diagonal but you would have to get used the Left/ Right reversed image.

Joplin

This one should work:

http://www.agenaastro.com/Antares-90-deg-Hybrid-Mirror-Diagonal-MSDH-p/odia-an-msdh.htm

Joplin

I've never compared these scopes side by side but I have used both of them. I would pick the C8 w/ XLT coatings. The central obstruction on the VMC200L is huge (40%) and the thick spider vanes are a distraction on many objects. The C8 is also easier to collimate since there is only one set of collimation screws for the secondary mirror vs. 3 sets on the VMC200L. It's also easier to find accessories / focusers for the C8 if needed. You would think that the VMC200L would cool down faster but the one I had didn't - it had annoying tube/ mirror currents visible for about 2+ hours on a cool winter night. I think this was due to the closed back design of the scope. As far as optical performance the VMC200L is good but the C8's I've looked through that were collimated did just as well or better. If you were planning to do just astrophotograpy then the VC200L (not the VMC200L) may be a better option than the C8.

Joplin

The only DED model that Vixen made (that I'm aware of) was the DED 108SS. Here's a description from a dealer website:

The Vixen DED 108SS telescope is a high perfomance apochromatic refractor with a double ED objective in a three-group, four-element lens system.One of the ED lenses is in a two-element objective lens, and another is set in the rear of the tube SPECIFICATIONS Objective lens (primary mirror) 108mm double ED Apochromatic Focal length 540mm.

The design is similar to the Takahashi FSQ-106, as far as I know it is apetzval design.
The ED114SS is a different design and more info can be found in this classifieds ad:

http://www.astromart.com/classifieds/details.asp?classified_id=331405

Neither of these scopes is made by Vixen any longer. This F8 offering is interesting but it has yet to be imported to the U.S. :

http://blogs.yahoo.co.jp/solunarneo/35581372.html

Joplin

A 2" to SCT thread adapter like this one should work fine:

http://www.agenaastro.com/Agena-2-SCT-Thread-Adapter-p/paar-ag-ff060-2.htm

Joplin

I find this site easier to use than fiddling with the light pollution overlays on google earth. The only disadvantage is that you have to find the site by zooming in rather than searching for a specific location.

http://www.jshine.net/astronomy/dark_sky/

Joplin

That image looks pretty normal for that length of exposure. From my area which is usually about mag 5.5 on a good night I usually don't bother with exposures over 1 min. with my 20D. Usually if I use an 80mm F6 refractor and the 20D I will start seeing sky fog after about 30 sec. at ISO 800. If I go to a darker site then the exposures can be quite a bit longer. The dust specks on the sensor can be cleaned off by using the sensor cleaning mode on the camera and special sensor swabs made for that purpose:

http://www.photosol.com/swabproduct.htm

I haven't gotten around to cleaning my 20D sensor with these but I really need to since there are quite a few dust specks visible.

I'm not up to date on Registax so hopefully someone else can answer that question.

Joplin