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Best portable mount for C9.25

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#1 dweller25

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Posted 28 February 2009 - 04:19 AM

I currently use a HEQ5/Sirius mount for my C9.25 for visual planetary observing. The mount JUST manages even with upgraded 2" legs and additional chain supports around the base of the legs.

I'm looking to upgrade to a mount that is between the weight of the HEQ5/Sirius and EQ6/Atlas. The EQ6 is too heavy for my bad back.

Takahashi is too expensive - so does anyone think a Losmandy GM8 or Vixen GPD2 would be better - more stable - than my current HEQ5/Sirius.

Thanks in advance.

#2 Patrick

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Posted 28 February 2009 - 07:39 AM

Hi Dweller,

Are you using anti-vibration pads under your mount? They might make the difference you're looking for.

The GM8 is rated about the same as the Sirius mount, and the GPD2 has a weight rating less the Sirius. Essentially, they are all in the same approximate class, so I wouldn't consider either of them as an upgrade to the other.

I think the CGEM would be the next step up in weight class, but it's overall physical weight is comparable to the EQ6 class mounts.

Again, I'd try anti-vibration pads first.

Regards,

Patrick

#3 Telescopeman54

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Posted 28 February 2009 - 07:51 AM

Do you wish to use it for AP or are you only doing visual work? The Mini Tower has been used by many visual observers with a C9.25. If you are interested in a GEM then you are kind of stuck with the CG5/EQ5 class or the larger EQ-6/Atlas class of mount.

Steve

#4 johnfdean

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Posted 01 March 2009 - 11:38 PM

I don't normally have a high opinon of anti-vibration pads, but under the circumstances, I have to agree with Patrick.

#5 Miguel Lopes

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Posted 02 March 2009 - 06:46 AM

Vixen SXD is very light and very, very stable for a C9.25.

A small trick is to use the tripod in its lower position and observe with a small camping chair.

#6 Luigi

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Posted 02 March 2009 - 08:48 AM

I'm a bit suprised you find the Sirius so woefully lacking. One thing to look for with these mounts is flex in the dovetail. A long vixen style dovetail can add quite a bit of flex to the system. Getting a stiffer dovetail or backing it up with an additional bar can help. I don't understand the chain around the tripod legs setup. One thing is to be sure the legs are angled out as far as they can go. The spreader on these tripods serves that function but I find it best to iterate by tightening it, spreading the legs and retightening it. Also, keep the legs shorter than fully extended if you can.

#7 Lane

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Posted 02 March 2009 - 10:23 AM

I got a Sirius mount and then purchased a C9.25. I then put the C9.25 in the closet for about 8 months and did not use it until I finally got the CGEM. It is not a pleasant experience trying to use a C9.25 on a Sirius mount.
On the Sirius without vibration suppression pads it has a 4 second damping time and that is with only a red dot finder and small 1.25 accessories attached. With vibration suppression pads that drops to 2.5 seconds. But when I try to use my 2" diagonal and 2" eyepieces it goes right back up to 4 seconds even with the pads. I also got an ADM saddle plate and bought a Losmandy dovetail bar and the result was that the damping time actually went up not down. The larger dovetail might be more stable than the vixen style dovetail, but the added weight offsets that benefit. So there are only 2 solutions, get a C8 which works fine on the Sirius mount or get a bigger mount. If you have a bad back I would suggest going to the C8. If you are going to go for a bigger mount you might be interested to know that the CGEM head weighs less than the Atlas and yet it has a better damping time.

#8 dweller25

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Posted 02 March 2009 - 01:58 PM

Hmmmm - CGEM - didn't think about that one - thanks.

#9 Miguel Lopes

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Posted 02 March 2009 - 03:24 PM

Also, buy a Baader dovetail for the C9.25. It fits in the Losmandy screws, while having the Vixen profile. Increases the stability of the mount.

#10 J_D_Metzger

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Posted 02 March 2009 - 09:47 PM

Hmmmm - CGEM - didn't think about that one - thanks.


If the EQ-6 is too heavy for your bad back, I wouldn't recommend the CGEM. The mount head is over 40 lbs...

#11 dweller25

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Posted 03 March 2009 - 04:29 AM

I think I will stick with the HEQ5/Sirius mount as the CGEM weighs the same as the EQ6/Atlas.

I do use vibration supression pads and I do have a Baader dovetail fitted, to be honest neither made any improvement to the vibrations. The 2" tripod I use is from the CG5 so is an upgrade over the original 1.75" legs. As suggested I observe sitting down so the legs have minimal extension - around 2".

I think I have to accept that the C9.25 is a little heavy for the HEQ5, however it's quite portable so I will just have to compromise.

Thanks for all the advice.

#12 Lane

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Posted 03 March 2009 - 04:33 AM

Actually I weighed the CGEM mount head with the counterweight bar removed and it was only 38 lbs. Compare that to the Atlas (EQ-6) which is suppose to be closer to 45 lbs. But even 38 lbs is a lot when you are having back trouble. The Sirius and the C8 make a nice combination and the heaviest component is less than 30 lbs, whenever my back is giving me trouble that is what I use.

#13 Luigi

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Posted 03 March 2009 - 07:26 AM

The Sirius should work, and many people have been happy with the C925 on a CG5. I recently got a CG5 to replace my G11 when I downsized OTAs because of its relatively light weight and good performance. It works very well with my 15+ lb OTAs for planetary obeserving.

#14 RAKing

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Posted 03 March 2009 - 07:34 AM

Actually I weighed the CGEM mount head with the counterweight bar removed and it was only 38 lbs. Compare that to the Atlas (EQ-6) which is suppose to be closer to 45 lbs. But even 38 lbs is a lot when you are having back trouble. The Sirius and the C8 make a nice combination and the heaviest component is less than 30 lbs, whenever my back is giving me trouble that is what I use.


My Atlas weighed 36 pounds, but that was too heavy for my back, so I downsized to the Losmandy GM-8.

The easy trick for the GM-8 is to use an Astro-Physics Portable Pier (or a G-11 tripod). This really stabilizes things and the C925 works great with this setup. The all up weight of my C925 is 25 pounds, ready to go, and I use two 7.5 pound counterweights with the GM-8.

The GM-8 only weighs 21 pounds. :cool:

Ron

#15 Lane

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Posted 03 March 2009 - 08:37 AM

The real problem with trying to make a decision like this based on CN comments is that no one gathers any objective data. People use phrases like "it works well for me", "it has almost no vibration", etc. What exactly that means depends on the person writing it. I was looking though this guys SN10 last year and its damping time was somewhere around 6 seconds. He was actually standing there bragging about how stable the configuration was. So what would be nice is for people to get a stopwatch, a high power eyepiece, thump the scope and start the stopwatch and wait for every little vibration to stop before stopping the stopwatch. Then we have objective data on which to base a buying decision. Then you can decide what is too much vibration for your personal taste. For me less than a second is great, 1 to 2 seconds is good, I can live with 2.5 seconds if I have to, but anything over that and I am getting a bigger mount.

#16 NHRob

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Posted 03 March 2009 - 12:51 PM

Lane,
Good points. Also .. what mag is it running at?

damping time of 2 sec with a low-power eyepiece is not good enough if you want to be running at 200-300X on planets most of the time.

Rob

#17 dweller25

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Posted 03 March 2009 - 02:10 PM

Just timed the damp down time - at x235 it is 1 second whilst focusing - which makes it hard to focus, otherwise it's very steady when I don't touch it.

PS - I have a Scopestuff plastic focuser fitted - the old peanut butter cap trick !! which really has helped.

#18 Lane

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Posted 03 March 2009 - 02:38 PM

Ok deweller25 - even I am not picky :shocked: one second is pretty hard to beat. If I load my C9.25 up with accessories so the weight is around 26 lbs I am getting just under 2 seconds of vibration on a CGEM and I am perfectly happy with that (that is with a set of celestron vibration suppression pads). My ED80 actually has 0 vibration damping time even without vibration suppression pads on both the Sirius and the CGEM. It looks to me like that is what you are after, but you will probably have to go to CGE and a C9.25 to accomplish that and of course that isn't very portable. Frankly the CGEM isn't really all that portable either, not like a Sirius anyway.

#19 Lane

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Posted 03 March 2009 - 02:44 PM

Lane,
Good points. Also .. what mag is it running at?

damping time of 2 sec with a low-power eyepiece is not good enough if you want to be running at 200-300X on planets most of the time.

Rob


I agree, I usually check damping time by aiming a spot with several stars in the field of view and bump to about 200x. I think when some people say their scope doesn't have a bad damping time it is exactly because of what you said, they are probably at 40x and it just doesn't matter as much at that kind of magnification. But if the point is to help other people with their buying decisions then that isn't very helpful.

#20 dweller25

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Posted 03 March 2009 - 03:21 PM

Ok deweller25 - even I am not picky :shocked: one second is pretty hard to beat. If I load my C9.25 up with accessories so the weight is around 26 lbs I am getting just under 2 seconds of vibration on a CGEM and I am perfectly happy with that (that is with a set of celestron vibration suppression pads). My ED80 actually has 0 vibration damping time even without vibration suppression pads on both the Sirius and the CGEM. It looks to me like that is what you are after, but you will probably have to go to CGE and a C9.25 to accomplish that and of course that isn't very portable. Frankly the CGEM isn't really all that portable either, not like a Sirius anyway.


Oh :o

Sounds like my setup is quite good then :foreheadslap:

Thanks for the feedback.






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