DSO AP with a wedge - why not?

[Guest]

Indeed, it looks good. Do you have any trouble with distortion over time or in the damp?

Olly

Actually no, I thought I would, but it has been there for 3 years although always covered with a heavy duty waterproof cover when not in use, so never got really wet. And it is made of very high quality hardwood, I have never had to re align it, and with autoguiding works very very well.

Am thinking of building an obsy around it this year.

MM

[Moonshane]

would a long focal length SCT (on whatever mount) be very suitable for small, bright planetary nebulae imaging?

[Psychobilly]

IIRC the wedge align function gave me a measured error of less than 3 arcmins... I had preset the wedge angle using a wixey angle guage...

If you in a fixed location then the wedge alignment only needs to be done once and checked periodically. ..

For me my lowest southerly horizon is about 10 degrees either side.of the meidian... with our central heating flue bang in thd middle... so the wedge mounted fork was a godsend in allowing me to image through the meridian with ease...

I also have a couple of Skywatcher mounts EQ-6 and EQ-3 Pro's an Astrotrac and various other GEM and Alt/Az mounts I can use either on the pier thats outside the obs or when away from home...

Peter....

Badly typed on my Galaxay S4 in Tapatalk4
 

[ollypenrice]

would a long focal length SCT (on whatever mount) be very suitable for small, bright planetary nebulae imaging?

Yes. Ideal. They have the focal length and the small object size means that quality fall off at the edge of field (afflicting standard SCTs) won't impact on the target.

Olly

[Luke]

I just wanted to chip in with something that I feel applies to a lot of equipment.

If you have many of the most talented folks using different equipment, then it's not surprising if the bulk of the best work comes from different equipment. It does not necessarily mean that the different equipment is vastly superior.

Myself, I did find my C11 a bit of a handful on an NEQ6. But really, I think pretty much every image posted on SGL is beyond my wildest dreams when I first got into this hobby. Tim's recent Rosette image is absolutely staggering, how he did not require a space telescope I cannot fathom (or did he buy the one from FLO?).

I guess it comes down to price, expectations, convenience, determination and perhaps a few other factors thrown in?

[ollypenrice]

Just one other small point. Using a Crayford or other aftermarket focuser is a good idea but has no connection with mirror flop. The amount of mirror flop depends on the scope used. Some have mirror locks or aftermarked spring loaded devices which can be quite effective but an OAG has to be the best solution with a reflector. That's what we use on Yves' 14 inch cat.

I'd have a flipless fork or arm mount in a flash if a good one were available for the kit I use. The Mesu number one is no longer made, though. http://www.astro-imaging.com/Equipment/Mesu_Mount_Engels.pdf Different, isn't it! The M Uno has to be worth a look, too, for smaller scopes. http://www.iankingimaging.com/show_product.php?id=1489

Olly

[MartinB]

Just one other small point. Using a Crayford or other aftermarket focuser is a good idea but has no connection with mirror flop. The amount of mirror flop depends on the scope used. Some have mirror locks or aftermarked spring loaded devices which can be quite effective but an OAG has to be the best solution with a reflector. That's what we use on Yves' 14 inch cat.

I'd have a flipless fork or arm mount in a flash if a good one were available for the kit I use. The Mesu number one is no longer made, though. http://www.astro-imaging.com/Equipment/Mesu_Mount_Engels.pdf Different, isn't it! The M Uno has to be worth a look, too, for smaller scopes. http://www.iankingimaging.com/show_product.php?id=1489

Olly

I think that's pretty much what I said Olly.  The change of focuser gets rid of image shift.

The M Uno is seriously tempting for me, not because of any problems with my SCT and mirror flop but because my dome has a very narrow aperture which means after an automated meridian flip my scope is pointing at the obsy roof!  I can go some way past the meridian usually generally I have to stop the imaging run in the middle of the night which can be very frustrating.  As it is, I'm currently trying to avoid spending more money!!

[Davey-T]

Thanks again for all your replies. I welcome them all regardless of which sidee of the fence you sit on. Sounds to be that AP on a wedge is doable, albeit a lot harder and seemingly more time consuming and frustrating than with an EQ mount.

Situation I'm in is that my obsy is very small (only 6x6) and I don't really have the option of having more than 1 set up. I want to keep the CPC1100 on the fork mount as I think observing will always be what I do most. However I'd still like to dabble in a bit if imaging which is why I thought mounting an ED80 on top would be the best solution. I appreciate I may not get top notch results, but id be happy with any of the results posted on this thread that were done on a wedge to be honest so that may be the best option for me. Even if it is more difficult!

The CPC1100 is already set up semi-permanently in the obsy so won't require too much readjusting very often once properly aligned hopefully and I do plan on adding a pier at some point this year as well.

I'm still not certain what to do but I do feel better placed to make an more informed decision having posted the question so once again thank you ALL for your input.

James

P.S. forks rule!! Ha ha

That's a good point James, my obs'y is only  6 X 6 and the fork mounted SCT  with dew sheild can cover the sky from side to side with plenty of clearance, don't think the same would be true of an EQ mount chucking itself about

Dave

[ollypenrice]

I think that's pretty much what I said Olly.  The change of focuser gets rid of image shift.

The M Uno is seriously tempting for me, not because of any problems with my SCT and mirror flop but because my dome has a very narrow aperture which means after an automated meridian flip my scope is pointing at the obsy roof!  I can go some way past the meridian usually generally I have to stop the imaging run in the middle of the night which can be very frustrating.  As it is, I'm currently trying to avoid spending more money!!

Agreed. I was responding to a point made by MM rather by you on that one, Martin.

Ah, I see the issue with the narrow dome opening. Curses! That's a pest. The M Uno would solve the problem. Would it carry your SCT?

I would like simply to remove the flip from the equation. If you have a premium mount which will just automate it and be done then fine, but they are expensive. So I positively like the fork mount in principle.

Also an issue with running well past the meridian on GEMs which will do that is that the scope becomes very low and can end up imaging the south or west wall...

Olly

[antimorris]

I just noticed this thread (sorry, a bit late to board the boat) but as I was mentioned a couple times in the thread I thought I should weigh in. 

Yes, a fork mount on a wedge is do-able. No, it as not as common or as easy (from what I hear) to go this route. 

I started with a CPC800 just on its normal Alt-Az mounting. I didn't want to spend a fortune as I was just learning the hobby so started that way constantly being told I couldn't do things with such a setup and set to prove them wrong. This soon became a trend. I eventually got a Milburn wedge (no, it was not cheap but I got it used so was cheap-ER and was still a lot less expensive than an EQ mount). I was then told by no less than a dozen people in my local astronomy group that I could NOT image with a wedge and fork mount. Challenge Accepted. I was not using an auto guider yet and after some fine-tuning with my polar alignment over a month or so eventually managed 3-5min subs (and occasionally longer) on the CPC800 WITHOUT an auto guider. It can be done. I do NOT recommend it. It was a pain in the rear and I did eventually buy a guider. I was still told that on the 2032mm lens on a wedge I couldn't do longer than 5 min subs or get decent images. Let me say this. This is patently wrong. I regularly do 10 min subs and often 20 min or more with this setup and I do not have a permanent observatory. I have my whole setup on wheels that lock and I roll it out from the garage every evening I am going to image, setup, polar align, and get going from scratch and still manage to do this. Olly has seen my setup (minus the wheels) and after a good bit of laughing at the sheer ridiculousness of the setup as I was getting it all going finally agreed that it could be done as well. A large SCT fork-mount on a wedge may not be the simplest, but for me it was the most economical as I used what I already had and saved for bits to add as I went (wedge, then auto guider, then OAG, then a piggy-back 80mm EON, etc). Yes, I even piggyback an 80mm refractor and use the CPC as the tracking mount for most of my images. I am a bit mad, but didn't have a fortune to spend so was willing to put in the time to figure out exactly how to get my setup to do what I wanted and, for me, it works. From what I am told over and over and over again, this is NOT the norm. Especially considering the C11 would make any of the issues I had with the C8 exponentially worse due to the longer focal length, I am certain it could be done, but maybe not the ideal setup (unless you are mad like me, I personally LOVE my wedged setup)

I am firmly in the camp of, YES it CAN be done but if you can afford an EQ mount then save yourself the hassle of figuring out this setup and just go with that. If you have the parts (such as already have the fork mount and don't want to de-fork it, etc, etc) then a few hundred dollar wedge is much cheaper than a few thousand dollar EQ mount, so if you can have a little bit of patience you can save a ton of money. 

Those are my two cents, happy to answer any questions/comments though.

[AstroJOE]

Thanks for posting this I really enjoyed reading it. It sounds like my curcumstances are similar to yours and I also share the same stubbornness to 'prove people wrong'. When I posted the original question I was hoping to get responses like this. I was still pretty much stuck on buying a wedge and then, as you say, adding an an OAG a bit later on (not too much later on). Your post has certainly given me added confidence to stick to the game plan though! I'm still very much a beginner and loving every miniscule improvement I'm able to achieve. May be one day ill give in and het myself an EQ mount but for now I'm digging my heels firmly in.

Thanks again.

[Davey-T]

As Anna says it's fine if you like challenge, I can do 30min subs with my Meade LX200 on a wedge with OAG, took a lot of tuning though and definately only possible if permanently mounted.

Dave

30min sub of NGC2359 not very good cos it's low down in LP.

[Padraig]

On 3 January 2014 at 11:28, MagnaMan said:

Check out my crude wedge Olly, cost £20 to build and is superb, never had to adjust in 3 years on the pier, and took about 25mins to initially align.

http://www.ollyspages.co.uk/p/diy-equipment.html

Half way down page

Who Needs a mega wedge of any kind, after using this one, never in my life would I spend the money needed to buy a wedge, so I do agree with you on that, "don't buy one build one" it's better and cheaper, and if it does not work, can't see why it wouldn't, you haven't wasted any money.

MM

Home made wedge…Ingenious ?

[cjdawson]

As a Meade LX-90 Owner.  I'd also agree that it's not a good setup for a starter.   Looking at the kit that is coming out these days, I too would recommend someone not follow the path that I did when I got into AP.   The setup that I have is difficult to get working just right and takes ages to get working.  That said, I bought my equipment in 2001 and have gotten some great images.   I'm still learning and am still not to the point of wanting to change my equipment yet.   I'm sure that day will come and when it does, I'll be looking to go down the refractor route rather than the route that I've taken.

Until then, I'm happy to take up the challange of taking images with an 8" f10 scope.

 

The things that I find are issues....

1. wobble.  This is increased when you put the scope on a wedge (when tripod mounted), you can get dampeners that go under the tripod legs, this helps.   But it's also best not to touch the scope for a few seconds before an image sequence.

2. PA error - it's worth taking the time to get his right before imaging,  I still struggle with this one.

3. PEC - Autoguiding is a must for long exposures.  Don't forget that once you've taken the image