Posts Made By: Joplin Motisher-Chittenden

Walter,

I had a similar experience a few days ago while it was still clear in SC. We usually have terrible seeing, the only time the air seems to get stable is when there is light morning fog which scatters some light. I had left my 10" F6 newtonian out on the deck to stablize for a few hours, then set it up around 4:30 and observed until dawn. The views were similar to what you described, except the GRS was on the far side of Jupiter. The highlight was watching Io and Ganymede pass each other just 2" apart. The huge difference in diameter was obvious between the two at high power. The seeing got better as twilight crept in and eventually washed out the finer details on Jupiter and Saturn. Hopefully the weather will clear up here soon so I can get some more viewing in.

Clear Skies,

Joplin

Greg -

The XR-P would be fine for short exposure astrophotography (few minutes or less). It has the necessary "B" or "bulb" setting for long exposures but most likely requires batteries to function during long exposures, which can get expensive (particularly since the XR-P takes four small button cells or two lithiums, twice as many as most older cameras). The easy way to tell if it requires batteries on the B setting is to take them out, turn on the camera, and see if it will release on B (most likely it won't and the release will be locked out.)
Having said that, if you just want to try some piggyback shots or lunar and planetary stuff, it will work just fine. Long exposure shots through a telescope (prime focus) are difficult without a bunch of other guiding equipment, etc. A camera that will work without batteries on B is the Ricoh KR-5 series, which can be found dirt cheap.
Here is a link to an online copy of the XR-P manual in case you don't have one.

Joplin

Debbie,

For CCD or digital camera astrophotography, a 2" focuser will work just fine. For full frame 35mm film prime focus astrophography, a 2.7" is preferable to avoid vignetting at the corners of the frame. What is most important is that the focuser is solidly built with no slop in the mechanism or sag in the drawtube when holding equipment. A lock screw to prevent creeping of focus after it is set is also essential.

Clear Skies,

Joplin

Matthew,

I would suggest joining the Yahoo LXD55 group (an excellent resource for these scopes) and posting your question thereas well since quite a few people with that same scope subscribe to it. I'm not personally familiar with goto scopes but I have heard that the LXD55 mount can be really finicky when it comes to alignment procedures; if you describe the setup process you used in detail hopefully someone there will have a solution. I did see one recent post claiming that aligning with polaris and then using a single star alignment yielded more accurate goto's so that may be worth a try.

Clear Skies,

Joplin

Jeff,

I'm not absolutely sure but I think that Discovery Telescopes' equatorial mount is the same as the Orion Skyview deluxe. They sell a dual axis drive for it but it is $229, a bit steep considering the cost of the mount. I would check with them to see if it is indeed the same mount. Their website is http://www.discovery-telescopes.com.

Clear Skies,

Joplin

Carlos,

I'd like to get copies of the templates as well. Email is joplinn at charter dot net Thanks in advance,

Joplin

The OM-1 was designed to use a PX-625 mercury battery which put out exactly 1.35 volts. In fact earlier cameras like the OM-1 relied on the extremely stable voltage of the mercury cell for an accurate reading. Mercury cells were outlawed years ago due to environmental concerns, leaving silver oxide, zinc air, and alkaline batteries as options for these cameras.
Unfortunately silver oxides are 1.55 volts, zinc air cells are 1.4 volts, and alkalines are supposed to be 1.5 volts but drop rapidly over time. Therefore, none of these will give a reading as accurate as one of the original mercury cell. Wein has come up with a solution that uses a zinc air cell that is supposedly somehow reduced to the proper 1.35 volts, but I have heard varying reports of success (some claim up to one stop exposure error with this cell in the OM-1)
The other option is to use an MR9 microcircuit voltage reducing battery adapter (preferably with a silver oxide cell). It is expensive though, but it has the advantage that you can find the 1.55 volt S-76 batteries that go in it in a lot of places - like walmart :-)

link to MR9 adapter: http://www.classic-cameras.com/MR-9.htm

link to Wein PX-625 replacement:
http://www.adoramaphoto.com/catalog.tpl?op=details&sid=10368725418735479&sku=BYPX625W

Clear Skies,

Joplin

Here is a link to a site with the adapters you need:

http://www.astrovid.com/adapters.htm

I would consider using a SCT to T adapter along with a C to T mount adapter because all the connections would be secure so there would be less chance of dropping the CCD camera. You probably already have the SCT to T-thread adapter if you have done conventional astrophotography with a 35mm SLR.
The C to T mount adapter can also be ordered online for a few bucks more through Edmund Scientific here:
http://www.edmundoptics.com/IOD/DisplayProduct.cfm?productid=1316

Clear Skies,

Joplin

I'll comment on the off-axis performance of the Siebert standard eyepieces (I own a 7mm Siebert standard). In my 80mm F8 apo refractor, the field size is about 40', the moon takes up 30' and is barley sharp at it's limb when centered in the eyepiece. I would estimate the critically sharp area at 27' or about 44 degrees of the 65 degree field of view. When combined with 2x shorty 3 element barlow, the sharpness increases a great deal, to about 58 degrees of the 65 degree field of view.
I use it in conjuction with the barlow most of the time, so it performs quite well. Eye placement is critical to avoid false color, this seems to be due to the large eye lens as compared to a plossl or ortho. The coatings on it can't compete with multicoating though and I have noticed ghosting on brighter objects, particulary when used without the barlow on a 10" newtonian.
Rather than a Focal Reducer, I would see about setting up the Nexstar for 2" viewing with a quality diagonal and a good widefield eyepice. The Proxima 31mm comes to mind, it's about $100 used on astromart. The view through a 70+ degree fov 2" eyepiece is amazing. I would skip the Siebert 21mm and go with an Apogee 20mm widescan (which will have slightly less fov, but it will be much sharper at the edges). For higher power, the U.O. 9mm ortho would be a great choice.

Clear Skies,

Joplin

I'd go for a Borg 76mm ED, it's in the middle of your price range ($800 new) and is part of a very adaptable system. It is very lightweight, you could mount it on a nexstar 80 mount if you decide you want goto (there is an inexpensive adapter made by Borg for this purpose). The best part is that if decide that you need more aperture, you can upgrade to the 100ED optics without selling the whole scope. I would definitely stick with a shorter focal length instrument since you already have a long focus instrument. Another option would be an Intes MN56, which would definitely give you the best planetary views at this price point and be light enough to work with the GP (not exactly 2 minute setup though). Just thought I'd drop in these suggestions before the Stellarvue people chime in :-)

Clear Skies,

Joplin