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Re: [APML]: Mounts
Hello skyshooter,
I could not resist responding to your comments about the AP1200 mount. I own
the AP QSP 1200 (stepper motor, non-go-to mount, 1 year old). It supports a 7"
f/7, 80mm guidescope, plus 46 lbs of counterweight. It's the system responsible
for producing the image on pgs 60/61 in the March S&T.
Some comments about the mounts operation:
1. The fact that the RA and DEC housings attach and break apart with a simple
dovetail connection is a big plus for portability. Especially for a total
equatorial head weight exceeding 60 lb. Each piece comes apart into easily
manageable pieces.
2. The polar alignment scope really works. With the factory adjustments, I
minimized my drift alignment times to 30 minutes total. There are minor
adjustment that you can make yourself to get the polar scope even more accurate.
Some users have even reported the elimination of drift alignment once the
polarscope is calibrated precisely "on-axis" with the mount.
3. Tracking accuracy seems to be limited to +/- 5 arc seconds. I see no
improvement using the PEC feature on the drive corrector. Using the ST-4, pixel
error is typically 0/0, 0/1.
4. The 7-inch and all the equipment, including counterweight is pushing close to
100 lbs. Dampening time is under 1/2 second with a slight tap on the 7"
telescope drawtube. I think considerable improvement in stiffness could be made
by using a heavier walled pedestal tube assembly. I use the 40" pedestal.
5. Manual motions are butter smooth. You have a fine range of RA and DEC clutch
adjustments (4 per axis) that allow for the "feel" that you want. When you lock
these guys down, nothing moves!
6. The hand control/drive corrector is a bit clumsy to hold. So, I just plug in
my Losmandy hand control (GM8/G11) into the CCD terminal, and use this palm
sized box for positioning at the camera.
7. Mount setup time to camera ready is 60 minutes.
8. In conditions of sub arcsecond seeing, at 400X and higher, experienced
observers can see how the stepper motors cause a resonating vibration in the
stellar or planetary image. At first I thought this was poor seeing until I
slewed an image of Jupiter across the field at 1X and noticed how "clean" the
image became. I understand that some of the CCD folks complained to Roland
about the stepper bounce which ultimately lead to the servo motor upgrade.
When seeing deteriorates to 1 arcsecond or worse, the stepper bounce is not
visible. Sub arcsecond seeing is often typical at my observing conditions, so
this has limited the overall exceptional performance of the 7" refractor.
9. Several friends own the equally impressive QMD 900 mount. I highly recommend
it to those who spend much of their time observing and casually approach
astrophotography.
10. Finally, and most important, in 20 years of astrophotography I have not
used a better mount for equipment support and long exposure imaging.
ciao
jg
______________________________ Reply Separator _________________________________
Subject: [APML]: Mounts
Author: Non-HP-skyshooter (skyshooter@mindspring.com) at HP-Boise,mimegw2
Date: 2/9/98 4:04 PM
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To all Astrophotographers looking for a new mount.
AstroPhysics Goto Mounts
I have been getting a alot of E mails asking me about the Astrophysics Mounts on
display at Winter Star Party. I am writing this information so you can make a d
ecision if you want to purchase the mount the AP1200 or AP900 mounts.
I setup next to the Astrophysics folks so I could watch them assemble the mount
s. The 1200 pier is 10² in diameter and light considering it1s size. Next the Ge
rman equatorial head which comes in two pieces were put on the pier and both uni
ts attached .The scope was set into the rings and tightened in place. The mount
and scope were extremely solid. I tried to wiggle the counterweight shaft but th
ere was no movement.
I1m no stranger to strong mounts having owned a few myself but this mount the AP
1200 was in a league above anything I have owned. The big test would come as nig
ht grew nearer. I helped the owner of the mount a fellow named Charles who is de
signer of APs new Digital Sky Voice software. Charles had the mount position fac
ing North. He then used the hand controller to position to a star over head and
then told the mount what star it was pointing to. He told me he could do all t
his with the voice software or with the keypad unit. He then told the mount to g
o to Polaris he used the mounts fine tune manual controls to center Polaris in t
he eyepiece. This procedure was done a total of 3 times.
Test 1 he asked the mount to find M42. With a 19mm eyepiece in the scope {AP180E
DF7² F7} M42 was dead Center in the eyepiece. I suggested let1s go from horiz
on to horizon and see how accurate it1s pointing ability is. Every object was de
ad center. Based on my past experience with goto scopes. I would have had to en
gage the High Precession Pointing accuracy to get this close. Even then the obje
ct was never dead center like this mount is.
Test 2 would be the drive accuracy. What better way to test it then to take a u
nguided CCD exposure. We selected 5 minutes exposures using a KAF 1300 chip. The
first exposure showed perfect round stars with the intended object in the cente
r of the chip.
We took a total of 10 exposure over the night every image showed perfect trackin
g. This mount has the best tracking accuracy I have ever seen. I have never seen
a mount that was capable of doing a 5 minute unguided CCD exposure with perfect
stars especially one that didn1t even have a star drift alignment done.
This was just unbelievable for me to imagine. I1m a proficient astrophotographer
and CCD imager. It usually takes me a minimum of 30 minutes to Star Drift to a
perfect alignment.
If your passion is CCD Imaging or Astrophotography there is nothing on the marke
t in this price range that works as well as these mounts. I can1t wait for mine
to arrive!
Ian Turner
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Ian Turner
Astrophoto and CCD Imaging Tips
http://www.geocities.com/CapeCanaveral/Hangar/7247/
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