Telescope Reviews: Observing Jupiter with the Paracorr inline.

Last night, the moon was dimming out my favorite DSOs, so I decided to observe Jupiter and run some eyepiece tests.

I had carefully checked and tweaked my XT12i collimation shortly after sunset, and had it right on!

Initial testing showed that the seeing conditions produced the best results at Mags. from Approx. 200x to 250x.

First eyepiece up was my 7mm BO/TMB which by itself in my F/4.9 XT12i gave me 214x.

As expected the image was sharp and clear, although the usual TMB scatter was noticed as Jupiter first drifted into the 60 degree AFOV. from the edge of the AFOV. This scatter does not seem to be a problem unless Jupiter was very close to the edge of the FOV, at which time it threw annoying light rays across the FOV.

As Jupiter drifted further into the FOV, this was no longer distracting

Next up was my Nagler 12T4 by itself, at 125x, and barlowed at 250x, using my GSO 2"ED 2x.

I like using my barlowed Naglers for planetary observing to take advantage of the extra drift time afforded by the Naglers 82 degree AFOV. No scatter was observed using the Nagler barlowed, or by itself!

The resolution and contrast of Jupiter's fine details which included the great red spot, and a moon in transit was excellent, but I felt that my 7mm BO/TMB just edged out the 12mm Nagler if one was really being critical!

I did interchange my 2.2x Shorty Plus, as well as my TeleVue 2.5x along with the GSO 2"ED 2x, just to get a feel for any changes or improvments in contrast.

All of the barlows gave excellent results, and I really didn't see any difference in contrast or resolution between my barlows!

I expect that this last comment will cause the TeleVue barlow purists to shake their heads and grind their teeth. For the record, my eyes when last tested, six months ago, were 10/10 for my dominant left eye, and 20/20 for my right eye...LOL!

Having bumped up the Mag. to 300x using my BO/ TMB 5mm, as well as my 12mm T4 barlowed with the TeleVue 2.5 x for a Mag. of 312X, I saw that seeing conditions this night really wouldn't support 300X observing.

I decided to concentrate my testing at 250X, but to reach this level of magnification with my 7mm BO/TMB, I had to take advantage of the .15x magnification of my TeleVue tunable Paracorr , which gives me 246X with the 7mm BO/TMB.

I had been happily switching back and forth for Approx. one hour before I inserted the Paracorr, and when I did, I immediately noticed that I was seeing the sharpest and highest contrast image of Jupiter so far observed!

I immediately switched over to the 12T4 2x barlowed, and although while still impressive, the image did not show the fine detail and contrast to the same degree as did the 7mm with the Paracorr!

Remember, I was really being critical , splitting hairs, and repeated these tests back and forth many times over the evening.

Having previously measured mechanical clearances, I carefully slipped the GSO 2" barlow into the Paracorr and then added the 12T4.

The resultant Mag. of 287X was just to high for the night's seeing conditions, and I couldn't draw any conclusions from this test, but I will try it again when the seeing supports 300x.

Cheers!

12" F/4.9 Intelliscope with COL

10" F/5.0 Coast Instrument Treckerscope,circa 1956

Stratus 35mm. Naglers 22T4, 17T4, and 12T4. BO/TMB 7mm and 5mm. TeleVue Paracorr

Barlows: GSO 2"ED 2x, Orion Shorty Plus 2.2x, TeleVue 2.5x

Binocs: Vixen 11x80, Oberwerk 15x70,Zeiss/Hensoldt 7x50, USN/Bausch and Lomb 7x50, Swarovski 8x30W
Bob

Edited by Bob W6PU (08/12/08 06:07 PM)