What a great night
Posted 24 August 2013 - 09:29 PM
As the subject said "What a great night. The sky was crystal clear. It was so clear that you could not see the beam from my green laser pointer. however all that glitters is not gold. The Manchester lights and lights from the Manchester airport were still there doing their thing.
Got the scope out early. Just as darkness was settling in and did the alignment. Then I started my Go To's with mixed success. "Mixed", Is maybe to strong a word. I would say the 98% of my objects were in the field of view and several of them were almost dead center. There were however, maybe 3 or 4 that weren't even close namely Albireo and M-13 and that puzzles the be devil out of me. With all the others so good why those few that were off.
Unfortunately around 9:45 My back started giving me problems so I packed up and called it a night before I could do that "Improving Pointing accuracy". Be that as it may I'm more than delighted with tonights session.
I've got to ad this P.S.
I was looking at a faint Globular and I can't remember which one but it was in Aquilla when a new neighbor and son stopped by and asked, "How are the stars" so I responded , "Come take a look" I explained what they were looking at but I don't think they were impressed. I then said, I'll get a brighter one", so I plugged in M-5. The scope started it's slew and their eyes opened up like saucers and their chin dropped figuratively at least 6".
They were impressed and when they looked there was M-5 almost dead center they were really inmpressed.... What a feeling
Posted 24 August 2013 - 09:46 PM
Sounds like your alignment was close, maybe you have some backlash this is common with these mounts.
Posted 24 August 2013 - 10:36 PM
I do sit, but you know when you slew to an object you usually have to get op and move the chair, and yes I feel I had a great night.
Posted 25 August 2013 - 12:30 AM
Yeah I was just asking because when I stand and have to bend over to look in the EP my back starts to kill me with an a hour.
Posted 25 August 2013 - 03:48 AM
With regard to your 'scope's GoTo accuracy, that sounds a whole lot better ! I've no explanation for why M13 and Albireo were adrift from your EP's FOV while M5; in loosely the same region of the sky; was "spot on", but there are of course, several additional means available to you whereby you can bring about greater accuracy when you're up and running.
T don't think backlash has any effect on the GoTo slew itself and I assume that by now you have optimised this, but you might, (if you don't already do so), use the "Calibrate GoTo " feature in the "Utilities" menu.
Paraphrasing from Mike Swanson's excellent book, "The Nexstar User's Guide":-
"This feature effectively calculates the amount of distance and time it takes for the mount to complete its final slow GoTo when slewing to an object according to the load on and balance of the OTA".
"GoTo Calibrate" takes into account any slight imbalances and consequently changes the final GoTo distance to compensate".
So, when you switch on your 'scope, and before aligning it, go into the Utilities part of the menu and scroll down until you reach this "Calibrate GoTo" feature. It may not solve the slight problems you're still experiencing but it certainly can do no harm.
Additionally, don't forget that if you 'scope appears to be less accurate, particularly in one area of the sky as your last session appears to have shown, (i.e. a lesser accuracy within that close region of the sky where M13 and Albireo are to found), then perhaps the application of the "Sync" feature within your HC's menu may help to gain greater accuracy within that region.
And on the same theme, if you cannot find a particularly faint object, (in as much as you are not sure whether it's in your EP's FOV or not), the "Precise GoTo" feature will normally place it centrally.
Hoping this helps a little further,
Posted 25 August 2013 - 08:24 AM
Thanks for great report!
Not sure what time of night you were viewing, but M13 and Albireo are pretty high in the sky during normal viewing hours these days. Alt/Az mounts do a poor job when getting close to zenith so that may have been the problem.
Posted 25 August 2013 - 11:02 AM
According to Stellarium based calculations, (given a 5 hour difference between the UK, (currently UT+1 hour), and Litchfield, NH.), I'd suggest that at Fred's location ca. 43 degs. North: 71 degs. West, Albireo reached a max. altitude of ca.75 degs. at ca. 22:06h. NH time/02:06h. UT. on the night of the 24rd.
Likewise, M13 reached its max. altitude, due South, at ca. 07:16h. NH. time/23:16h. UT of 83 degs: both therefore, relatively close to the Zenith if the above were the approximate observation times.
Fred ? Give us a clue ! At what time approx. where you looking for and "missing" Albireo/M13.
Posted 25 August 2013 - 03:48 PM
Posted 25 August 2013 - 04:48 PM
Would these either of these altitudes be likely to adversely affect the accuracy of GoTo slews ? Personally I think not, but .........
Posted 26 August 2013 - 08:26 AM
Posted 27 August 2013 - 01:52 AM
Then yes, as both Dan and James have suggested, trying to access objects on or very close to the Zenith, will indeed have a marked, adverse effect on GoTo accuracy.
Wait till such "Celestials" are at a lower altitude.
It's much easier on the back too !