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Old 15-01-2010, 11:06 PM
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floyd_2 (Dean)
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Guidescope for a 10" SCT - Is it worth getting a decent refractor?

I've been a visual astronomer for about 20 years. My current telescope is a 10" Meade LX200GPS SCT on a Meade ultrawedge.

I've started heading down the astrophotography path with a Meade DSI Pro II camera and f/3.3 reducer, but up until recently, have been taking photos in Alt/Az. Now I'm on a wedge, I plan to increase my exposures if the clouds ever clear, and am considering getting a guidescope and autoguider in the coming months.

I was hoping that I might be able to get some advice from the group on guidescope choice. I'm thinking of using a Starshoot autoguider on an 80mm refractor and was wondering if I should consider buying a higher quality guidescope to enable me to do some widefield photography in the future as well (using the SCT as the guider). Is it commonplace to use guidescopes for widefield, or do the majority of people end up just using them for guiding only?

I guess I may use the guidescope as a grab and go from time to time, but for the most part I'm set up to do imaging / visual from my backyard only (in the suburbs) where an 80mm won't really punch through the sky glow very well.

I know that weight is something that I have to keep in mind with a fork mount as well. I intend to use a 2D counterweight and am wondering what weight guidescope an LX200GPS would support for DSO photography work, as this may help me to avoid going over the top with refractor choice.

I'm mindful of buying a guidescope that will suit me into the future, and intend to eventually purchase a more advanced camera as my photography improves and my needs increase.

Any hints that you may have if you've already been down this path would be gratefully received.

Dean
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Old 15-01-2010, 11:30 PM
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Tandum (Robin)
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Hi Dean, I just added a Tak FS-60 as a guider for my FS-102 here with thoughts of using it as a wide fielder at some stage. It's guiding the mount for the first time tonight

I also have a stellarvue F60M3 coming as a guider for my 10" newt. It's a 60mm straight through finder with a 2" helical focuser on the end. I was looking at cutting down the weight with this one as it weighs about .5kg.
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Old 16-01-2010, 06:20 AM
gbeal
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Given the weight and weight distribution limits I see with the fork SCT my suggestion is the finder/guider. I have a cobbled 8x50 finder that has the guide camera (SXV guide-head) unceremoniously installed in place of the eyepiece. Works like a charm at the 800mm focal length of my refractor, as well as at the 1800mm focal length of my Mak. Try that first unless you really want that grab and go addition. If that is the case, the FS60 is where I am headed next.
Gary
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Old 16-01-2010, 07:06 AM
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multiweb (Marc)
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Yep. I second that. In most case an 8x50 finder wil do just fine.
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Old 16-01-2010, 10:48 AM
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mtodman (Matt)
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Hi there Dean,
My previous setup was a wedge mounted 10" LX200 GPS which was guided by a skywatcher ED80 / Meade DSI Pro II combo. I found this to work very well once I had everything well balanced (an absolute must for this setup).
My intention was to do exactly as you have indicated, ie use the ED80 for some wide field work. I was happy with the results.

Cheers

Matt
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Old 16-01-2010, 12:43 PM
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citivolus (Ric)
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An ED80 will piggyback just fine on a wedge mounted LX200GPS. Set your maximum slew rate back a few due to the increased mass that you are swinging around, to make things easier on your motors at the start of the slew.

I had an ED80 on a 10" LX200GPS using the Losmandy D style dovetail plate and guide rings, and a 2D counterweight system. It was quite stable in that configuration. Some shots for you to get and idea of how it was set up are here.

Regards,
Eric
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Old 17-01-2010, 09:35 AM
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floyd_2 (Dean)
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Thanks very much for your replies Tandum, Gary, Multiweb, Matt and Eric. All great reading. I really appreciated the photos of your setup Eric. I can feel myself being drawn down the 80mm path, and even looked significantly into the Megrez 88 last night - which doesn't look to be the goods for imaging unfortunately.

It was a long cloudy night last night, as it usually is on the weekends in Sydney, so I put in many hours of research. I found many an excellent thread on the forums here that helped me to build a better picture of what I can do, and what I should steer clear of. I can't believe the wealth of experience on these forums.

I now have a spreadsheet comparing pricing and features of:
William Optics ZenithStar 80II
Orion EON 80mm
Stellarvue SV80ED Raptor Carbon Fibre
William Optics Megrez 90
William Optics Megrez 88

with the ZenithStar 80II, Orion EON 80mm and Stellarvue SV80ED Raptor being of the greatest interest to me. A lot of this comes down to them having the greatest FOV.

I ran the specs of each scope through Ron Wodaski's CCD Calculator to see how they would compare FOV wise with the camera I currently have, and also compared to what I'm already doing on the LX200GPS at f/3.3.

I considered using my existing camera as a guide camera on a dedicated cheaper guide-only scope, and grabbing a QHY8 (for example) to see if that would better suit the bill for widefield imaging as well. However, that ended up being the most expensive option and had a few downsides - like not having the added benefit of a grab and go scope at the end of the day.

I've priced up rings, dovetails, 2D weight systems, field flatteners, guide cameras and extension drawtubes as well. As I'm sure so many others have done before me, I've started drowning in research. At least, however, plonking it all into a single spreadsheet for comparison is helping things along to an eventual conclusion. After all, daddy wants a new toy

At the end of it all, it looks like I'll be up for between about $1500 (ZS80II plus all ancillary gear) and $2000 (Megrez90 plus all gear).

I think I might go and do some more research

Dean
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Old 18-01-2010, 04:21 PM
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citivolus (Ric)
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Hi again Dean.

One caution about the larger scopes is that going from 80 to 90mm may be too much piggyback load, as it will likely add 2kg or so plus extra counterweight, plus it is pushed out further from the centre of mass. As long as you balance it all carefully before setting the clutch, and further reduce your maximum slew rate, you could probably get away with it, but it may exceed the manufacturer's recommended weight as well as increase guiding and vibration induced errors.

Regards,
Eric
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Old 18-01-2010, 04:33 PM
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floyd_2 (Dean)
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Thanks Eric. I was just speaking with Mick over at Bintel Sydney about the exact same thing, and I immediately discounted anything over 80mm as having the potential for too much trouble, and placing too much load on the mount. I'm looking further into the differences between the Orion EON 80mm and the William Optics ZenithStar 80II now - it's down to those two puppies!

Interestingly, the only information that I can find on the payload of the LX200GPS 10" mount states that the payload is 65lbs. Just the OTA is about 62lbs on the 10". If the rule of thumb is not to exceed 2/3 of the mount's payload if you're imaging...I'm over that already - straight out of the box.

I've noticed that there are a few people here who look to have been in my shoes in the past, and have ended up on a GEM. It has me wondering if I'm pushing a bad position, mount-wise, for imaging going down the path I'm headed down.

Dean
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Old 18-01-2010, 04:50 PM
el_draco (Rom)
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Guidescope

Quote:
Originally Posted by floyd_2 View Post
At the end of it all, it looks like I'll be up for between about $1500 (ZS80II plus all ancillary gear) and $2000 (Megrez90 plus all gear).

I think I might go and do some more research

Dean
Hi Dean. Faced the dilemma myself recently and ended up with a Megrez 90. Cost me about $1200 from memory, but I got a great guidescope and a grab and go that has a bit of grunt. I think it would be pretty heavy on a fork, mine is SBS. If you want a good option, there have been W.O. 66mm scope OTA's on eBay for about $460 on a regular basis, (New) from QLD for the last couple of months. Would have bought one, but missed out and was forced to go up to the 9omm Megrez.

IMHO, I'd always get a good quality scope over a poor quality scope for a number of reasons. With my current set up I can swap the imaging between the main scope and the guidescope at my leisure and I like that, alot!

NB. There's a good shot of M42 through a W.O. 66mm in the Deep Space section of IIS at the moment.
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Old 19-01-2010, 08:15 PM
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floyd_2 (Dean)
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Hi Rom,
and thanks for taking the time to let me know about your experiences. I'm sorely tempted by the Megrez 90, but it's just going to be too much weight and too large an instrument for my mount, unfortunately I used to own a TV101, and know that the extra 10mm of aperture in the 90 would make quite a difference.

I'm getting close to ordering a Stellarvue SV80ED Raptor (the carbon fibre one) after weeks of near constant deliberation, review reading, chatting with the guys at Bintel and talking with you all here. It's about 1kg lighter than any other 80mm ED, and comes with Stellarvue's reputation.

In the old days, this would have been quite an easy decision. But with a wife and cute daughter under my belt now, every cent counts. Wish me luck

Dean
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Old 22-01-2010, 03:30 PM
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floyd_2 (Dean)
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Just in case anyone was following this thread, or for future reference...the Stellarvue SVR80 Raptor should be arriving early next week from Optcorp. They were very easy to deal with. The Losmandy DA 125mm rings and dovetail plate, counterweight system, 2" extension tube, 2" diagonal for any visual work and Orion Starshoot autoguider all came today well packed from Bintel. I decided to order an Astrozap Focussing Cap for the Raptor as well, which should arrive on Monday.

As you can see, with such a booty inbound to Sydney you all know what's going to happen. I should have ordered an umbrella as well. At least we all made it past the new moon weekend (just)

Dean
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Old 25-01-2010, 10:01 PM
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floyd_2 (Dean)
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My new baby raptor arrived today. It shipped from Opt on Friday morning and arrived at my home this afternoon (Monday). In fact, I almost fell off my chair when Australia Post rang to tell me that they were at my front door. This is the first time EVER that Aus Post hasn't done a hit and run leaving a card in the letterbox in their wake.

The 80mm Raptor is very nice indeed. I managed to set it up for about 5 minutes before cloud enveloped my whole viewable sky. A quick peek at the moon through a 16mm nagler, and then a 9mm nagler showed super crisp views. The focuser is super smooth with zero slop, and there is surely no going back after using the fine focus. The finish of this scope is just excellent.

It came with a tube ring and RDF with multiple reticules too. All very nicely packed into a custom die cut foam lined carry-on luggage bag. The rail on the bottom of the tube ring is tapped for a standard tripod, which is great for grab'n'go viewing. Whilst a photo tripod isn't the best thing to use, it certainly serves its purpose when you want to travel light.

I noted that the 2" extension tube that I purchased didn't seem to cater for a 1 1/4" reducer, as the slot on the top edge (for the fixing screw on the reducer) wasn't there. So, the reducer needed for the guide camera wouldnt fit all the way down into the extension tube. A bit of time with a dremel fixed that problem.

I'm itching to take a look at the night sky with it properly before I mount it up and start using it as a guider. I wonder when the clouds will clear

Dean
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