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Topics - Jim Parker

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Eyepieces Questions & Recommendations / Planetary EPs for 130mm refractor
« on: December 29, 2017, 03:07:00 AM »
Hi all,

I just purchased a TS photoline 130 mm f/7 refractor and have been doing some research looking for a couple good planetary EPs for it. I'm not looking to spend a fortune, and all my reading indicated you don't need to on these types of EPs to get exceptional performance.

I'm willing to spend up to/around $100 per ep and would like the EP to have generous eye relief.

I've read some good reviews on the WO SPL, which I was thinking the 6 mm. I remember reading that the Orion edge-on planetary EPs are identical (I think maybe cheaper too). I figure if I really like it I can grab the 3 mm for those nights that the sky is exceptional. V

I did just pick up an 8.8mm ES 82 on the classified so I'll probably stay away from that FL. Anyway, just wanted I'd like to hear suggestions and options. Thanks!

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Hi,

I finally had a chance to test the April/May 2015 firmware upgrade of CEM60EC and see if it really improves the SDE. The conclusion is that, there appears to be no improvement, at least on my copy of CEM60EC. Note that all the firmware of my CEM60EC is the latest, and I did an RA encoder calibration right after the firmware upgrade. The guiding test immediately follows the upgrade and the encoder calibration. All guiding tests are conducted on stars of Dec of about +10 deg, which is in the middle between the celestial equator and zenith (Dec = +19 deg) for my location. To fine-sample the SDE, I used a 0.2 sec exposure time with sub-frame readout. The actual frame rate is about 0.33 sec per frame.

Please see the attached PDF. It has four PHD2 graphs, with guiding disabled. The first one is a pre-upgrade graph, and the p2p error was about 3 arcsec. The following three were taken last night. By eyeballing it and ignoring the long term trend, all three new graphs suggest a p2p error of also about 3 arcsec. In all cases, PHD2 reports rms of just above 1.0 arcsec, except for the one that shows a long term drift at the end.

A subtle difference is that in the first graph, the periodic behavior is very obvious and consistent. I remember it was like this in my other tests before the firmware upgrade. On the other hand, in the three new guiding graphs, sometimes the periodic behavior is apparent (like the last one) but sometimes it is almost not there. I am not sure whether this is something real in CEM60EC's behavior after the firmware upgrade, or its just atmospheric seeing (my site has exceptionally good seeing), or something else. If this is real, maybe CEM60EC is doing something to fight for the SDE, but obviously this doesn't quite improve the final performance (neither p2p nor rms).

This is disappointing, although this doesn't really impact my imaging under f=500mm.

For those interested in the PHD2 guide log, it's here:

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Hi . I would like to form this group with people who are trying to decide or who have these telescopes. Questions which I have in particular are the following.

1. Which mount would you recommend ?
2. Which brand name is best?
3. What aperture size, focal length combination is best for astrophotography?

Hoping you will join this discussion group

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Beginners Forum / Eyepiece Question,
« on: December 26, 2017, 10:53:34 PM »
Is the picture going to be brighter in an 82?? than at an 68???  Or is it the other way around?

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