DSO AP with a wedge - why not?

[AstroJOE]

Morning everyone, this is a question for the imagers amongst us really...

I have a CPC1100 which I love and use it mainly for visual at the moment. I intend doing some AP this year, that's my resolution anyway!! I don't want to take it off the fork mount as I think visual will always be my preference. Therefore I'm probably going to get a heavy duty wedge and mount an 80ED on tops of the OTA at some point.

My question therefore is what are the main challenges with using a wedge instead of an equatotial mount when imaging DSO's specifically and can these be overcome? Also will there be a significant difference in the quality of the DSO images I am able to take bearing in mind I'm probably only ever going to be an enthusiastic beginner rather than a hardened/professional imager!

If anyone has any DSO images taken on a wedge is love to see them!

James

[ollypenrice]

Anna Morris uses a Celestron fork mount on a Millburn wedge. Need one say more? However, this is not at the focal length of the C11. For me the deafening silence in terms of images posted from fork SCTs tells its own story. There are millions of fork SCTs out there. Where are the pictures?

The basic challenge doesn't arise from there being anything inherently wrong with a fork equatorial. It's an attractive idea done well by the M Uno, for instance. That has a single arm rather than a fork but it's the same thing really. The problem lies in trying to image at long focal lengths, especially with the tiny pixels of the 600D. Autoguiding errors need to be kept sub pixel and this will be a tall order for you on anything but a premium mount. The Celestron and Meade forks are a very long way from being premium. If I were to image with a C11 I'd be looking at a Mesu or 10 Micron or Astro Physics or Paramount. These are accurate mounts capable of handling the focal length involved.

Given the variable quality of the fork mounts the danger is simply this: you buy an expensive wedge (they cost a fortune!) and then you find that polar aligning and balancing are difficult and time consuming and, when you've done them, you don't achieve workable tracking. That spells time and money down the drain. I've been there courtesy of Meade.

You can buy an HEQ5 for the price of a decent wedge, put a short budget apo on it, and be confident that you'll be taking good astrophotos in very little time.

Olly

http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/22435624_WLMPTM#!i=2266922474&k=Sc3kgzc

[ronin]

Using a wedge shouldn't cause that much of a problem, that is after all what a pillar amounts to.

I guess that getting the wedge correctly polar aligned could be the main problem to contend with.

I presume that the CPC has the option to set the mount type to equitorial, think some of the newer ones don't.

[Davey-T]

I can image fine with a 100mm refractor piggy backed on fork mounted 10"SCT, not so easy imaging with the SCT, it definatley needs to be permanently mounted in an obs'y so it stays level and Polar aligned.

Image of Momkey face needed more subs but gives you an idea

Dave

PS forgot to mention I also had to strip and rebuild the mount

[ollypenrice]

Yes, I used to piggyback a small refractor on my wedge mounted SCT and it worked. But it's a very expensive way to mount a small refractor!

Using a wedge shouldn't cause that much of a problem, that is after all what a pillar amounts to.

I guess that getting the wedge correctly polar aligned could be the main problem to contend with.

I presume that the CPC has the option to set the mount type to equitorial, think some of the newer ones don't.

Using a wedge shouldn't cause a problem, I know. The trouble is, though, that it often does!

Olly

[Guest]

Anna Morris uses a Celestron fork mount on a Millburn wedge. Need one say more? However, this is not at the focal length of the C11. For me the deafening silence in terms of images posted from fork SCTs tells its own story. There are millions of fork SCTs out there. Where are the pictures?

The basic challenge doesn't arise from there being anything inherently wrong with a fork equatorial. It's an attractive idea done well by the M Uno, for instance. That has a single arm rather than a fork but it's the same thing really. The problem lies in trying to image at long focal lengths, especially with the tiny pixels of the 600D. Autoguiding errors need to be kept sub pixel and this will be a tall order for you on anything but a premium mount. The Celestron and Meade forks are a very long way from being premium. If I were to image with a C11 I'd be looking at a Mesu or 10 Micron or Astro Physics or Paramount. These are accurate mounts capable of handling the focal length involved.

Given the variable quality of the fork mounts the danger is simply this: you buy an expensive wedge (they cost a fortune!) and then you find that polar aligning and balancing are difficult and time consuming and, when you've done them, you don't achieve workable tracking. That spells time and money down the drain. I've been there courtesy of Meade.

You can buy an HEQ5 for the price of a decent wedge, put a short budget apo on it, and be confident that you'll be taking good astrophotos in very little time.

Olly

http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/22435624_WLMPTM#!i=2266922474&k=Sc3kgzc

"There are millions of fork SCTs out there. Where are the pictures"

This a line you have used a lot in forums Olly, I have read it numerous times written by you, and is getting a bit boring, if you take the time to look there are hundred of thousands of images taken with fork mounted SCT' s, I don't know why you always seem to dis the SCT, we haven't all got the money to invest in a multitude of different and expensive scopes, the SCT is a good basic starter for AP and visual, plus very good for planetary imaging, so a good all rounder for us beginners

I know you are a god around here for your work and pictures and I admire that, but you are totally wrong about this.

MM

[StuartJPP]

I know someone who is doing basically the same, not sure exact size of his SCT but it is has been a pain for him. The wedge is only part of the problem as he had to get some fairly costly weights to achieve balance. And to top it off there are certain objects he can't image because the camera and the forks don't work together well.

Of course if you can get the bits fairly cheapish it may be worth a try, even just to say you tried.

[Psychobilly]

I was in the fortunate position to be able to design, have fabricated and make the other bits and pieces neccesary to use my fork mounted CPC800 in my obs...

As it was a fixed location I didn't need to desing in 10's of degrees of adjustment in the wedge and so it was fairly easy to acomplish using opposing  jack  screws for +/- 1 degree at my latitude...

I also "fettled" the AZM bearings and on the mount as was able to get realiable 30 and 60 min guided  subs...

Most of the "SCT" imaging was with a Modified 350D then Modified 1000D usualy at f6.3 with  a dabble at Lunar &  Planetary at f20 and f30 using a DMK21AU04AS ...

It also was also used a fair bit of "frac" imaging with a range of piggybacked "budget" scopes Equinoxe66 &  Megrez 72, while guidign throug a 500mm f8 T-mount lens and Meade DSI IIc...

"Fully Loaded"....

Sky at Night CD Jul 2010 Moon 67 pane mosaic by psmithuk, on Flickr

Sky at Night CD Mar 2009 M33 by psmithuk, on Flickr

Sky at Night Mag Feb 2009 Flame HHN by psmithuk, on Flickr

Sky at Night Mag Jan 2009 NGC7000 & IC5070 by psmithuk, on Flickr

Sky at Night Mag POM Aug 2009 NGC6888 by psmithuk, on Flickr

Sky at Night Mag July 2010 B33 WF by psmithuk, on Flickr

I might try and dig out some of the other SCT images later

A 1800s (30 min) tracking test sub...  Flattener spacing wasn't that clever...

Mars at f30... IR pass an dodgy focusing...

Peter...

[MartinB]

"There are millions of fork SCTs out there. Where are the pictures"

This a line you have used a lot in forums Olly, I have read it numerous times written by you, and is getting a bit boring, if you take the time to look there are hundred of thousands of images taken with fork mounted SCT' s, I don't know why you always seem to dis the SCT, we haven't all got the money to invest in a multitude of different and expensive scopes, the SCT is a good basic starter for AP and visual, plus very good for planetary imaging, so a good all rounder for us beginners

I know you are a god around here for your work and pictures and I admire that, but you are totally wrong about this.

MM

Olly is stating the problems inherent in using fork mounted C11 for deep sky imaging, it certainly isn't a "good basic starter for AP".  However given that is is an excellent visual set up and an outstanding planetary imager it isn't surprising that people want to try it for deep sky imaging.  It's best that people know the issues so here goes:-

Focal length - the native focal length of a C11 is huge, you need high end  tracking and guiding to get round stars.  Also F10 makes it a slow set up which means longer exposures further aggravating the problem.  Fortunately help is at hand with a range of focal  reducers.  Favourite amongst these is the Celestron 0.63 reducer which can potentially bring the focal length down to around 1750mm (still long!).  You can get a Meade 0.33 reducer but this will only give a satisfactory image on a very small chip.

Field curvature -  an SCT doesn't give a flat field meaning that the whole of the field will not be in focus.  This can be reduced by using a reducer/flattener like the Celestron 0.63.  The spacing between the back of the reducer and the camera chip to produce a flat field is somewhere around 110mm, although in my experience the field still isn't flat over an APS sized chip.  Works well for a slightly smaller chip.  The weight of camera, filter wheel, off axis guider maybe, plus extenders is likely to case some flexure but less of an issue with sub APS sized chips.

Focuser - the standard focuser on an SCT moves the mirror and causes image shift.  This is a real pain in the neck.  The rate of shift is maximal when you first start moving the focuser in a new  direction and eventually becomes negligable whilst ever you focus in the same direction.  Unfortunately as soon as you go past the optimal focus point (which you need to do) the shift comes back with a vengeance as soon as you start to move in the opposite direction.  You get better with practice but it is a very tedious business.  Of course fitting a Crayford focuser helps resolve the problem but £££

Mirror flop - some scopes are worse than others.  My old NS8 was great and didn't need a mirror lock.  My Meade does.  The problem with mirror flop comes as the scope passes the meridian.  Movement of the mirror briefly messes up but is less of an issue with off axis guiding.

Wedges - the Celestron heavy duty wedge can drive you to madness.  You could spend a lifetime trying to achieve polar alignment the adjusters are so poor.  It is an unbelievably bad piece of engineering.  From what I can gather the Meade offerings aren't much better.  There are great wedges out there.  I had an APT wedge which was excellent and polar aligning was every bit as straight forward as an Eq mount, much easier than with a standard Eq6 in fact.  But quality wedges aren't cheap, best to look out for second hand offerings.

Tracking - the tracking of these Celestron and Meade forks has been much derided but my old Celestron Nexstar tracked nicely.  I was only just starting with guiding at the time but it didn't produce any big random errors and was fine.  However, I gather the quality of the gearing was dropped a little when the Nexstar was superceded by the CPC.  Periodic error can be corrected easily enough but big random errors can result in a mount being impossible to accurately guide.

My ultimate set up was an APT wedge, 8" Nexstar (nb much more manageable than a C11) with a Celestron 0.63 reducer, a standard focuser, Sx adaptive optics, Trutek filter wheel and an SX H9 camera.  Once you got to grips the the complexity of the adaptive optics unit this was a very effective imaging set up and I always felt the optics of the NS8 were excellent.

[Guest]

Olly is stating the problems inherent in using fork mounted C11 for deep sky imaging, it certainly isn't a "good basic starter for AP".  However given that is is an excellent visual set up and an outstanding planetary imager it isn't surprising that people want to try it for deep sky imaging.  It's best that people know the issues so here goes:-

Focal length - the native focal length of a C11 is huge, you need high end  tracking and guiding to get round stars.  Also F10 makes it a slow set up which means longer exposures further aggravating the problem.  Fortunately help is at hand with a range of focal  reducers.  Favourite amongst these is the Celestron 0.63 reducer which can potentially bring the focal length down to around 1750mm (still long!).  You can get a Meade 0.33 reducer but this will only give a satisfactory image on a very small chip.

Field curvature -  an SCT doesn't give a flat field meaning that the whole of the field will not be in focus.  This can be reduced by using a reducer/flattener like the Celestron 0.63.  The spacing between the back of the reducer and the camera chip to produce a flat field is somewhere around 110mm, although in my experience the field still isn't flat over an APS sized chip.  Works well for a slightly smaller chip.  The weight of camera, filter wheel, off axis guider maybe, plus extenders is likely to case some flexure but less of an issue with sub APS sized chips.

Focuser - the standard focuser on an SCT moves the mirror and causes image shift.  This is a real pain in the neck.  The rate of shift is maximal when you first start moving the focuser in a new  direction and eventually becomes negligable whilst ever you focus in the same direction.  Unfortunately as soon as you go past the optimal focus point (which you need to do) the shift comes back with a vengeance as soon as you start to move in the opposite direction.  You get better with practice but it is a very tedious business.  Of course fitting a Crayford focuser helps resolve the problem but £££

Mirror flop - some scopes are worse than others.  My old NS8 was great and didn't need a mirror lock.  My Meade does.  The problem with mirror flop comes as the scope passes the meridian.  Movement of the mirror briefly messes up but is less of an issue with off axis guiding.

Wedges - the Celestron heavy duty wedge can drive you to madness.  You could spend a lifetime trying to achieve polar alignment the adjusters are so poor.  It is an unbelievably bad piece of engineering.  From what I can gather the Meade offerings aren't much better.  There are great wedges out there.  I had an APT wedge which was excellent and polar aligning was every bit as straight forward as an Eq mount, much easier than with a standard Eq6 in fact.  But quality wedges aren't cheap, best to look out for second hand

Tracking - the tracking of these Celestron and Meade forks has been much derided but my old Celestron Nexstar tracked nicely.  I was only just starting with guiding at the time but it didn't produce any big random errors and was fine.  However, I gather the quality of the gearing was dropped a little when the Nexstar was superceded by the CPC.  Periodic error can be corrected easily enough but big random errors can result in a mount being impossible to accurately guide.

My ultimate set up was an APT wedge, 8" Nexstar (nb much more manageable than a C11) with a Celestron 0.63 reducer, a standard focuser, Sx adaptive optics, Trutek filter wheel and an SX H9 camera.  Once you got to grips the the complexity of the adaptive optics unit this was a very effective imaging set up and I always felt the optics of the NS8 were excellent.

M27.jpg

Well I use a meade LX90 on a homemade hardwood wedge, and with a tightening of the bearing in the scope I get 20 min subs no problem, with no mis shaped stars at all, I use the meade electric crayford style focuser so no mirror flop and a 6.3 reducer, a modded 1000D DSLR imaging camera, a skywatcher ST80 guide scope with an old meade DSI guide camera,You can't get much more basic than that, and I get myself great images, may not be good enough for magazines or up to Olly's standard, but that isn't what us amateurs are after, it is a hobby after all.

Sometimes I think people get wrapped up in the science of it all rather that get out and enjoy it.

I spent around £1000 on my set up

MM

[MartinB]

Well I use a meade LX90 on a homemade hardwood wedge, and with a tightening of the bearing in the scope I get 20 min subs no problem, with no mis shaped stars at all, I use the meade electric crayford style focuser so no mirror flop and a 6.3 reducer, a modded 1000D DSLR imaging camera, a skywatcher ST80 guide scope with an old meade DSI guide camera,You can't get much more basic than that, and I get myself great images, may not be good enough for magazines or up to Olly's standard, but that isn't what us amateurs are after, it is a hobby after all.

Sometimes I think people get wrapped up in the science of it all rather that get out and enjoy it.

I spent around £1000 on my set up

MM

As I was suggesting, it's doable.  Maybe you could post one of your pics to persuade Olly to change his view.

[AstroJOE]

Thank you for all of your replies so far, some very useful information which I will have to consider.

Whilst I don't want to start an EQ versus Wedge war it very interesting to hear the differing opinions. As I suggested in my original post I'm only ever likely to dabble in AP in an amateur way, more of a hobby (as MagnaMan suggests). Therefore it is particularly encouraging to see the image MagmaMan posted of the Monkey Face early on in the thread which was taken on a wedge. I'm no expert (as I think you're already probably aware) but to me it's a great image! May be not a magazine quality image, I don't know.... but as someone who is looking to get into AP as a beginner I would personally be over the moon to produce an image like this........watch this space!!

I agree the C11 has a fantastic reputation as a planetary imaging scope and I fully intend to use it for this, however as I also mentioned in my original post I will most likely mount an ED80 on the C11 and use that to image DSO's rather than the C11 itself..... at least that's what I wanted to do assuming it is possible?!? (Forgive me if I'm talking nonsense but that's what I assumed could be done).

Some brilliant images throughout this post so I haven't been put off by your initial post Olly, although it's definitely given me some food for thought!

Thank you once again for all your comments, very interesting stuff!

James

[Psychobilly]

I have my rough but functional Scrap Ally Wedge somewhere...  It was designed to fit between the CPC 800 and the Celstron Tripod.  Seeing as your "Nr Cardiff" I doubt if you lattitude is a lot different to mine and  you can "tweak" it I will dig out some pics and if it's any good to you then you can have it....

Just had a quick search and  and it looks like I already had the OBS setup by the tiem I joined SGL... I did go back to my first ever post in the process though... Ther ehaev been a few more since then... 

It means it may be harder for me to find a pic of it in use as it is several "PC's" ago...

Just had a thought after lookign at soem plans I put together for a couple os simple "wooden wedges" -  that It probably won't be any use to you as the CPC1100 is much bigger than the CPC800 so the scope Centre of Gravityy is very unlikely to be over the centre of the tripod and I wouldnt want the thing falling over....

Peter...

[AstroJOE]

I have my rough but functional Scrap Ally Wedge somewhere...  It was designed to fit between the CPC 800 and the Celstron Tripod.  Seeing as your "Nr Cardiff" I doubt if you lattitude is a lot different to mine and  you can "tweak" it I will dig out some pics and if it's any good to you then you can have it....

Just had a quick search and  and it looks like I already had the OBS setup by the tiem I joined SGL... I did go back to my first ever post in the process though... Ther ehaev been a few more since then... 

It means it may be harder for me to find a pic of it in use as it is several "PC's" ago...

Just had a thought after lookign at soem plans I put together for a couple os simple "wooden wedges" -  that It probably won't be any use to you as the CPC1100 is much bigger than the CPC800 so the scope Centre of Gravityy is very unlikely to be over the centre of the tripod and I wouldnt want the thing falling over....

Peter...,

Peter, thank you very much for the original offer but you're probably right, the CPC1100 is a big beast so the centre of gravity will be different. Vey kind of you to offer though. I'm in Miskin by Pontyclun BTW so 'Nr Cardiff' is only approximate, not far away though! 

[jackrussell0232]

James,

I have an LX90 SCT, and as a visual/planetary tool, I love it.  It was the first serious scope I bought, so I did some basic modded webcam and modded security cam astrophotography with it (10+ years ago).  I never managed a subframe longer than 60s, even at f3.3.  Eventually I piggy-backed a small refractor on it, and tried imaging through this too, but balancing the set up was quite involved, and there were many other drawbacks, which others have listed.

MM is entitled to his opinion, everyone on here is.  You can take deep space images with a fork mounted SCT, you can piggy-back a refractor on one - just like someone could have carved the presidents' faces into Mt Rushmore with a screwdriver, don't think it would be much fun though.  Using a piggy-backed refractor makes imaging both easier (shorter FL) and more difficult (balance and tracking and autoguiding through an SCT).

Good astrophotography is pretty hard already.  A number of things can make it very very hard:

wrong mount

wrong scope (slow or long focal length, or both)

insensitive cameras

(plus all the environmental stuff - LP, weather...)

I would keep the C11 for planetary imaging and visual work.  For the price of a good wedge you could get an EQ5. Put a short refractor on this and you'd be good to go, and likely to get plenty of good images.

I've seen loads of breathtaking images taken with ED80's on EQ5s.  

And I've seen plenty of deep sky images taken with SCTs - I just can't remember any of them.

JMHO,

Jack

PS (MM, I do like the look of your wedge though)

[AstroJOE]

Apologies to Davey-T - the impressive image of the Monkey Face taken on the fork-mount was his!!

[AstroJOE]

James,

I have an LX90 SCT, and as a visual/planetary tool, I love it.  It was the first serious scope I bought, so I did some basic modded webcam and modded security cam astrophotography with it (10+ years ago).  I never managed a subframe longer than 60s, even at f3.3.  Eventually I piggy-backed a small refractor on it, and tried imaging through this too, but balancing the set up was quite involved, and there were many other drawbacks, which others have listed.

MM is entitled to his opinion, everyone on here is.  You can take deep space images with a fork mounted SCT, you can piggy-back a refractor on one - just like someone could have carved the presidents' faces into Mt Rushmore with a screwdriver, don't think it would be much fun though.  Using a piggy-backed refractor makes imaging both easier (shorter FL) and more difficult (balance and tracking and autoguiding through an SCT).

Good astrophotography is pretty hard already.  A number of things can make it very very hard:

wrong mount

wrong scope (slow or long focal length, or both)

insensitive cameras

(plus all the environmental stuff - LP, weather...)

I would keep the C11 for planetary imaging and visual work.  For the price of a good wedge you could get an EQ5. Put a short refractor on this and you'd be good to go, and likely to get plenty of good images.

I've seen loads of breathtaking images taken with ED80's on EQ5s.  

And I've seen plenty of deep sky images taken with SCTs - I just can't remember any of them.

JMHO,

Jack

PS (MM, I do like the look of your wedge though)

 Thank you Jack, I may need to go back to the drawing board then after all!

[Merlin66]

Anything is possible!

Maurice has achieved some spectacular successes with his wedge mounted 12" Lx200. I used one for many years for spectroscopy - which IMHO is far more "challenging" than AP - finding and holding a target star image onto a 20 micron slit - at f10!!!!.

[Guest]

James,

I have an LX90 SCT, and as a visual/planetary tool, I love it.  It was the first serious scope I bought, so I did some basic modded webcam and modded security cam astrophotography with it (10+ years ago).  I never managed a subframe longer than 60s, even at f3.3.  Eventually I piggy-backed a small refractor on it, and tried imaging through this too, but balancing the set up was quite involved, and there were many other drawbacks, which others have listed.

MM is entitled to his opinion, everyone on here is.  You can take deep space images with a fork mounted SCT, you can piggy-back a refractor on one - just like someone could have carved the presidents' faces into Mt Rushmore with a screwdriver, don't think it would be much fun though.  Using a piggy-backed refractor makes imaging both easier (shorter FL) and more difficult (balance and tracking and autoguiding through an SCT).

Good astrophotography is pretty hard already.  A number of things can make it very very hard:

wrong mount

wrong scope (slow or long focal length, or both)

insensitive cameras

(plus all the environmental stuff - LP, weather...)

I would keep the C11 for planetary imaging and visual work.  For the price of a good wedge you could get an EQ5. Put a short refractor on this and you'd be good to go, and likely to get plenty of good images.

I've seen loads of breathtaking images taken with ED80's on EQ5s.  

And I've seen plenty of deep sky images taken with SCTs - I just can't remember any of them.

JMHO,

Jack

PS (MM, I do like the look of your wedge though)

Thanks

It works very well too, cost around £20 to make, it has been outside on a pier now for 3 years and still perfectly aligned.

Who needs to spend £300 on a mega wedge, not me and like I said earlier in this thread I have had up to 20 min guided subs from this.

Regards

MM

[Naemeth]

I think the reason why quite a few seasoned imagers recommend not to use SCTs is not that they are unusable, it's that for the cost of getting them to work (and the time spent) you would be far better off with a short semi-apo or apo. Which, from my understanding are pretty much maintenance free, don't tax their mounts or owners and are most forgiving of PA errors and guiding errors.

[smudgeball]

I think the reason why quite a few seasoned imagers recommend not to use SCTs is not that they are unusable, it's that for the cost of getting them to work (and the time spent) you would be far better off with a short semi-apo or apo. Which, from my understanding are pretty much maintenance free, don't tax their mounts or owners and are most forgiving of PA errors and guiding errors.

While there's no way I'd call myself "seasoned", the above exactly describes what I did.

I was visual with my 6SE and had tried a bit of piggyback imaging plus webcam for planets.

I'm now imaging with a WO Megrez 72 on a neq6pro and glad I took the time to decide what I was going to do.

Neil

[ollypenrice]

The opinions raised in this thread clearly indicate that using a wedge and fork is not always plain sailing. I personally know nine people who have given up on them. I don't known nine people who have moved to wedges from GEMs.

At no point have I said it can't be done, as my opening homage to Anna's imaging makes perfectly clear.

If somebody asks me whether I would recommend a fork and wedge I'm going to do what I always do and give an honest answer. I would not. If that's boring, sorry but it's a considered opinion. It isn't the only opinion, it is an opinion and not a fact, and those who disagree can says so. That's how forums work. I just had a flip over to CN to see if there were any fork SCT images on the first page of the DS imaging. There weren't. I stand by the belief that SCTs are under represented in terms of images published per scopes in circulation.

I can promise Martin that Celestron's wedge is unlikely to be worse than the Meade Super Wedge on which I wasted a fair old wedge  , even second hand. Any tightening of any bolt at any stage in the alignment procedure threw all previous adjustments out of kilter. This object consisted of a handful of crude castings with no machined surfaces in sight and slop in all directions. A disgrace. Again, as Martin said, if you buy a wedge buy a good one, but they are so expensive. I bet that Peter's, 'fixed' for latitude maybe by placing it on a couple of ballbearings and boling it down at each corner to control the tilt, would be far better than the standard ones.

Olly

[Guest]

The opinions raised in this thread clearly indicate that using a wedge and fork is not always plain sailing. I personally know nine people who have given up on them. I don't known nine people who have moved to wedges from GEMs.

At no point have I said it can't be done, as my opening homage to Anna's imaging makes perfectly clear.

If somebody asks me whether I would recommend a fork and wedge I'm going to do what I always do and give an honest answer. I would not. If that's boring, sorry but it's a considered opinion. It isn't the only opinion, it is an opinion and not a fact, and those who disagree can says so. That's how forums work. I just had a flip over to CN to see if there were any fork SCT images on the first page of the DS imaging. There weren't. I stand by the belief that SCTs are under represented in terms of images published per scopes in circulation.

I can promise Martin that Celestron's wedge is unlikely to be worse than the Meade Super Wedge on which I wasted a fair old wedge  , even second hand. Any tightening of any bolt at any stage in the alignment procedure threw all previous adjustments out of kilter. This object consisted of a handful of crude castings with no machined surfaces in sight and slop in all directions. A disgrace. Again, as Martin said, if you buy a wedge buy a good one, but they are so expensive. I bet that Peter's, 'fixed' for latitude maybe by placing it on a couple of ballbearings and boling it down at each corner to control the tilt, would be far better than the standard ones.

Olly

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

[ollypenrice]

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

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

Olly

[AstroJOE]

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