Fork mounts

[BobSki]

Is it possible to track objects using a fork mount?

I'm currently looking at a Meade telescope on a fork mount but wondered if anybody had used this setup to track objects for AP.

All the best

Bob

[Gazabone]

Hi Bob,

I assume you're talking about non goto mounts. If so, the only way I know of doing it is to put a wedge between the tripod and mount. They tend to be expensive but the good news is that if you're better at DIY than me, they are fairly easy to make yourself. Basically all they do is alter the angle of the fork mount to compensate for the latitude of your viewing. In essence it turns your mount into a sort of eq mount.

If you have a goto fork mount then it should be able to track anyway but won't adjust for field rotation which isn't a problem unless you're doing long exposure photography with it.

Hope that helps.

[BobSki]

Hi Gaza,

Thanks for your response.

I was looking at a meade LX90 currently for sale with its original tripod and fork mount. It is a GOTO mount but I was wondering how or if this type of mount could track an object for longer exposures. It doesn't look like it will, but hey, what do I know, I have never owned a scope before LOL

[damnut]

Hi Bobski,

I had Pete Sha's 10" lx200,  you should check his images. You do need an equatorial wedge these are readily available. You can also attach a field de-rotator.

See :--- http://www.themcdonalds.net/richard/index.php?title=Astrophotography_Equipment:_Mounts

[cfpendock]

 track an object for longer exposures. 

Sounds like you want to use the scope for photography.  Take care, I understand this scope has a focal ratio of f10 - very slow for astrophotography.  But not impossible - you need a wedge, as Gazabone said above, but even then it is not easy.  If you definitely want to pursue the astrophotography route, first read; "Making Every Photon Count", by Steve Richards and available from FLO who sponsor this forum.  This will introduce you to the basics of astrophotography, as well as explaining why the scope you are considering is not ideal for starting out on astrophotography.

Chris 

[Astroboffin]

hi,

I have the Meade LX90 and it sits on an Equatorial wedge and I image with it and get Subs of 20 mins no problem.

I guide it with a piggybacked small scope and use an SX Lodestar guide camera.

But I have to say that getting perfect balance is the key to guiding these mounts, get that right and it works a treat, get it wrong and you will be looking at a damaged scope, or at least the gears will be smashed.

If you just use without a wedge in ALT AZ mode, then you can't track for long, as you will get field rotation, so a wedge is the way to go.

Hope that helps

AB

[Gazabone]

Hi Bob,

Now that we know that you're looking at the photography bit, a few of us have mentioned field rotation, just thought it was worth checking that you know what is meant by that; would you like an explanation?  I've never owned a Meade and only had (literally) about 2 mins play with an 8" LX200 but you are considering a nice bit of kit. 

Cheers

Gareth

[BobSki]

Hi folks, I greatly appreciate your knowledge and help on this.

I am currently searching for my first scope. I have read no end of info on the different types of telescope and I must say the whole subject is quite complex.

As there is No such thing as an all-rounder scope, compromises have to be made, as such, the catadioptric type of telescope seems to combine most of the elements I "think" I want. I don't want to go smaller than an 8" though.

I am starting out with the mindset that observing will be the manin use of the telescope but I do have a Nikon D300 DSLR that I would probably like to use with it to take some photos of our celestial neighbours. So I would like, at some stage to be able to take some images.

i was first offered a Celestron C8 on a Super Polaris mount with several eye pieces, Solar filter upgraded motors and "Star Sensor 2000" for £500, However, this scope is 30yrs old and the star sensor unit is a discontinued item and spares are unavailable. so I considered £500 to much to risk as if the star sensor failed, which, after 30yrs, is highly likely, I'd have to fork out in the region of another £300 or so to replace it with a modern unit.

Then I came across an advert for a C9.25 on a CG5-GT mount, but from what I have read, the mount is probably not substantial enough for that scope size/weight.

Now I am looking at a second Meade LX90. A friend of mine has one and took a stunning (to me anyway) photograph of the moon.

So, while Astrophotography is not my main intention, I do like the idea of taking images of some nebulae, planets, moon, sun etc and I don't want to rule it out entirely by choosing the wrong mount.

My budget is limited, so I keep searching the "pre-loved" telescopes hoping to find one that will fulfill my requirements. If that Meade was on a better mount, I think I would have found what I am looking for. The C9.25 is the next closest but I see in your signature Gaza that you have what I think I am looking for, I am of course, referring to your C8 on the AVX mount

[ollypenrice]

DS imaging on a wedge is, in my opinion (and I've tried it), much harder than doing so on a GEM. DS imaging at slow F ratios is uncontrovertially much harder than at fast ones. DS imaging at long focal lengths is uncontrovertially much harder than doing so at short ones. In the case of the last two points this is especially true of DSLR cameras.

So if you go for an 8 inch SCT on a wedge you are stacking up all the difficulties in short order. Have a look at the DS imaging boards to see what most people are using.

Personally I think the wedge spoils the fork mount for visual observing, is not needed for fast frame planetary imaging and is very hard work for DS. I heartily wish I'd left mine as it was in Alt Az and used something smaller for DS imaging.

If you are mobile then it takes a long time to set up a wedge mount.

Olly

[Davey-T]

I have 10" Meade SCT  fork on a wedge permanently mounted and image OK with it. It is well suited to planetary and lunar imaging and with a CCD camera there are DSO targets that lend themselves to the long focal length / small field of view.

I never imaged successfully with it on a tripod and wouldn't recommend it as a first scope except for Solar System objects, as Olly says there are better ways to start out, a second hand EQ5 and a small refractor which you can use a DSLR with should keep you occupied for years especially with our weather

Dave

[BobSki]

Thank you gentlemen.

As it happens, I had been looking at refractors but thought the 8" SCT would be a bit more of an all-rounder, given that I do realise the true all-rounder does not exist.

[ollypenrice]

For me the thing that stops an SCT from being an all rounder is the focal length. The long focal length makes it a specialist rather than a gereralist scope. If there is an all rounder (big 'if'  ) then I'd say an 8 inch Newt around F5 would be the one. You can use it visually from fairly widefield to high power, you can use Powermates to do planetary imaging on it and it would be fast as a DS imager and have the kind of FL and bulk which an EQ6 can handle painlessly.

Olly

[mcolbert]

Bobski any possibility of buying the C9.25 ota only?  Then search for a suitable mount/tripod.

michael

[BobSki]

Hello Olly. The thing about an 8" Newt is the size. It is so big and bulky. It tends to put me off a bit as I am unsure if I could manage it on my own.

To buy a C9.25 on a vex mount is a few hundred over my budget. The trouble is, to find a second hand setup is difficult. If I did buy the OTA second hand I would probably have to buy the VX mount new and that would put me back in the same budgetary issue.

[damnut]

Hi Bobski,

I have a 150mm Mak, 152mm 127mm 120mm and a st120 refractors.  I still lust after my 10"sct, why, on a fork mount with a wide angle 30mm you rarely needed goto, moving across the sky was a doddle. For me it was the best compromise between apperture and mount, but thats me!

[BobSki]

LOL Damn nut.... you must be running up and down a lign of scopes already, do you REALLY want to add another one....just buy and send it to me, I'lllet you know how good a 10" SCT looks!

[dph1nm]

Imaging with long focal length scopes is fine if you are able/willing to bin up your camera (in hardware - so tricky with DSLRs) and don't want to take wide fields shots.

NigelM

[Astroboffin]

DS imaging on a wedge is, in my opinion (and I've tried it), much harder than doing so on a GEM. DS imaging at slow F ratios is uncontrovertially much harder than at fast ones. DS imaging at long focal lengths is uncontrovertially much harder than doing so at short ones. In the case of the last two points this is especially true of DSLR cameras.

So if you go for an 8 inch SCT on a wedge you are stacking up all the difficulties in short order. Have a look at the DS imaging boards to see what most people are using.

Personally I think the wedge spoils the fork mount for visual observing, is not needed for fast frame planetary imaging and is very hard work for DS. I heartily wish I'd left mine as it was in Alt Az and used something smaller for DS imaging.

If you are mobile then it takes a long time to set up a wedge mount.

Olly

Sorry Olly, but I disagree with a couple of things, I am a complete beginner really and find my Mead LX90 a pleasure to image with, as long as it is on the wedge and a focal reducer is used, (with a DSLR for imaging or a big chipped CCD) I have gotten 20 min subs with no issues what so ever, the secret is perfect balance and all pressure off the gears of the mount.

I have used an Equatorial once that I borrowed, and to be completely honest did not find it that much easier, certainly not enough to warrant the extra £'s involved in owning one.

I think fork mounted SCT scopes have gotten a lot of bad press, and not deservedly, a little patience is all that is needed.

Sorry to disagree

Regards

AB

[Davey-T]

I've done 30min subs on the Thors Helmet, low down so not easy, using my 10" SCT fork / wedge.

A lot of bad press was originally caused by the crappy plastic gears and the way the worm motor ass'y was mounted.

It's still not a do it all scope but excellent for the things it excels at and with a piggy backed refractor, which it carries with ease I can image pretty much anything I wan't too.

Can even stick the LS60 on it at the same time as well. 

Dave

[schmeah]

I imaged for years on a fork 10" LX200R @ f/10 with subs as long as 20 minutes. Getting an OAG made all the difference in the world with my setup. And piggybacking a refractor turns it into an all around setup. In fact my one and only APOD was on this fork mounted setup. Although there are challenges with the fork mount, the simplicity, no flip etc, is what led me to get a single arm fork variant (M Uno) when I upgraded.

Derek

[ollypenrice]

Sorry Olly, but I disagree with a couple of things, I am a complete beginner really and find my Mead LX90 a pleasure to image with, as long as it is on the wedge and a focal reducer is used, (with a DSLR for imaging or a big chipped CCD) I have gotten 20 min subs with no issues what so ever, the secret is perfect balance and all pressure off the gears of the mount.

I have used an Equatorial once that I borrowed, and to be completely honest did not find it that much easier, certainly not enough to warrant the extra £'s involved in owning one.

I think fork mounted SCT scopes have gotten a lot of bad press, and not deservedly, a little patience is all that is needed.

Sorry to disagree

Regards

AB

Don't apologise for disagreeing! That's what forums are all about. You are one of a not insignificant number of people who have succeeded in getting the fork SCT to work for DS imaging. However, my experience was less positive and I personally know at least half a dozen imagers who gave up trying with this system and a fair few more who succeeded but still moved to GEMs because they needed less persistent tinkering.

BTW, perfect balance didn't sove my problems. There was simply too much backlash in the drives of my LX200 and attempts to create an adjustable imbalance in order to keep on one side of mesh didn't work out for me. There is a lot of variety in the QC of mass produced mounts and this may explain the inconsistencies in peopls' findings.

Olly

[Astroboffin]

Don't apologise for disagreeing! That's what forums are all about. You are one of a not insignificant number of people who have succeeded in getting the fork SCT to work for DS imaging. However, my experience was less positive and I personally know at least half a dozen imagers who gave up trying with this system and a fair few more who succeeded but still moved to GEMs because they needed less persistent tinkering.

BTW, perfect balance didn't sove my problems. There was simply too much backlash in the drives of my LX200 and attempts to create an adjustable imbalance in order to keep on one side of mesh didn't work out for me. There is a lot of variety in the QC of mass produced mounts and this may explain the inconsistencies in peopls' findings.

Olly

Hi,

I agree about the backlash and that should be set to zero in the mount settings, also what I found useful was to tighten up the motor gear mounting bolts, as for some strange reason, when these scopes were manufactured they were left quite loose and contributed to a lot of backlash, before I did this i had a few small issues, so I went against the advice of certain people who are known as gods with these mounts, and tightened them, they said leave the motor mount bolts well alone.

I could tell straight away after tightening them, that there was a considerable difference, and have never looked back.

Regards

AB

[Davey-T]

Had mine all to bits and rebuilt to minimise backlash and other issues, also think they need to be permanently mounted and PA for successful imaging.

Dave

[damnut]

@Davey-T thats a great setup

@bobski- know what the lx 200 it's like, but have two piers no running around...

[BobSki]

Blimey, those are some impressive setups guys.

I have settled my mind and will receive my new Celestron C8 Newt on an Advanced VX Mount  TOMORROW.