Looking after your cat.

[Apostate]

Hello chaps

May I first apologise for the poor weather in the West Midlands over the next few weeks; I have just taken possession of a new scope.

Said scope is a Meade LX200 EMC 10".  It was offered to me during a hunt for a good 8" SCT for planetary imaging.  I am chuffed to bits with it but have realised that the arrangements I had for storing and mounting my scope are going to need to change.

So, if you don't mind, I have a few questions for those of you who keep big cats at home.

My SW Explorer 150P has lived in the corner of the living room atop an old model black HEQ5, itself on a black SW pier.  No counterweights attached because the tube weighs next to nothing and the mount and pier (which weighs a flipping ton) are not letting a 150mm newtonian push them around.  The non-astronomer in my relationship does not mind this arrangement since she thinks it looks good in the corner of the room - lucky me.

My first question is, if I find enough counterweights to balance the LX200 and given that the vixen dovetail saddle has been replaced with a ADM Losmandy saddle to suit, is it safe to hoist a scope that size up there and leave it mounted (and balanced) as permanent storage?

Having hefted the scope and thought about my trusty HEQ5 I have decided that, despite being within payload limit, the HEQ5 is going to have to make way for something burlier - I'm thinking an EQ6 syntrek.  Is this the most sensible option?

In order to fund the new mount my HEQ5, the pillar, the Explorer 150p and all the assorted newtonian paraphernalia that I have acquired is being sold.  Of these bits and pieces I am thinking that I may still have a use for my laser collimator and my Baader MPCC (coma corrector) are either of these pieces of kit worth keeping?

Now to the mystical SCT thread; I am considering a reasonably priced focuser (crayford?) to which a JMI autofocus motor or similar may be attached (or possibly a home-brew solution) but is this actually a better option than motorising the standard focuser? Motorised focus is necessary - l don't think I can tolerate manual focus for very long.  I honestly have only a vague idea of how an SCT focuses - I know the primary moves back and forth, but how it does this without whacking the scope out of collimation must be an expensive piece of precision engineering to stick on the back of a telescope when a crayford, it seems, does the same job?

Also on the shopping list, since my baby DSO catcher is being moved on, is a focal reducer.  Which of the multitude available should I buy if I buy new?  Or secondhand? would this screw onto the scope's SCT thread before or after the focuser?

Also, given that I image DSOs with a APS-C chipped DSLR am I going to encounter issues with light clipping?  Am I going to be better off finding some imaging solution to suit a 1.25" holder?

Very many thanks for your attention, guys.

S

[DRT]

I keep my CPC1100 in a 50 gallon Stanley tool box. It just fits with no room to spare.

The tripod sits beside the box.

I don't do imaging so can't help with your other questions, sorry.

[ChrisLX200]

I think I lost track of all the questions in this one...

I use a Losmandy dovetail bar (home-made, stretches from rear cell to front cell), my OTA usually just sits horizontal on a shelf but it would be equally happy on the mount.

For a long time I used the stock focus knob, then I motorised the stock knob, and very recently fitted a rack and pinion focuser with a stepper motor so I can remote autofocus. My LX200 EMC is probably the same as yours and the internal focus mechanism is far less sophisticated than you might imagine. The biggest problem with the Meade is that it moves the primary by pushing it off-center which does lead to mirror shift, plus the primary carrier is not a close fit on the primary baffle tube so mirror 'flop' becomes apparent as you traverse the meridian. Therefore stabilising the mirror (if you have nothing else then use the transport bolt trick to hold it in place) and using a secondary focuser offers a good improvement.

I have an f/6.3 reducer but be aware that will vignette on larger sensors - not sure if you can get away with one as large as APS-C but I'm hoping it will be OK (or at least be correctable) with my Atik 490. My reducer is fitted between focuser and visual back.

For colimating you need to aquire the skills to perform a Star Test, and fit larger thumb screws in place of the stock 3 Allen screws. A simple laser is not much help with SCT but you can get holographic types that do work. However, the final arbiter for correct colimation is always a star test and for me that's all I ever use. With practice it takes a minute or two at most.

ChrisH

[Apostate]

Thanks guys

Apologies for the number of questions - I figured that asking them all in one place would cut down on redundant topics..

I'll bear the toolbox solution in mind if the scope gets evicted from the living room - I may build a small shed in the garden to roll it and the tripod into and keep the remainder of my kit in the captain's chest it lives in now.

Chris - good to hear from somebody with the exact same scope - how is it to live with?  Also - regarding focusing - what is the transport bolt trick?

As for the vignette caused by the focal reducer; would the MPCC help with this, do you think?  It's optimised for F4.5-6 newtonians but as (to my eye) issue looks to be similar might the MPCC help correct it? 

I do intend to star collimate 'in the field' and I know that a laser collimator is no use employed as normal (I thought I saw an article about using the laser output from the front of the scope to check for faults in the optics, but I probably dreamt it).  Does anybody have any time for artificial stars for day-time ball-park collimation prior to an evening's observation or imaging, or am I holding over newtonian habits and SCTs do not go out far enough during normal transport and use? Given that my scope has just done 200 miles strapped into the back seat of my car moving at 90 mph I am expecting to have to make reasonably significant corrections - would you expect similar?

Sorry to bang on - what are your thoughts on an EQ6 as a new mount?  Is it sufficient or should I think about a CGEM.  I'm reluctant to go for the latter as I really like using EQMOD.

Cheers

Simon

[Peter Drew]

Simon. To add to the comprehensive reply you already had, I used a 12" SCT on a EQ6 Pro to good effect, steadier and more reliable than the fork mount.    

[ChrisLX200]

Thanks guys

Apologies for the number of questions - I figured that asking them all in one place would cut down on redundant topics..

I'll bear the toolbox solution in mind if the scope gets evicted from the living room - I may build a small shed in the garden to roll it and the tripod into and keep the remainder of my kit in the captain's chest it lives in now.

Chris - good to hear from somebody with the exact same scope - how is it to live with?  Also - regarding focusing - what is the transport bolt trick?

As for the vignette caused by the focal reducer; would the MPCC help with this, do you think?  It's optimised for F4.5-6 newtonians but as (to my eye) issue looks to be similar might the MPCC help correct it? 

I do intend to star collimate 'in the field' and I know that a laser collimator is no use employed as normal (I thought I saw an article about using the laser output from the front of the scope to check for faults in the optics, but I probably dreamt it).  Does anybody have any time for artificial stars for day-time ball-park collimation prior to an evening's observation or imaging, or am I holding over newtonian habits and SCTs do not go out far enough during normal transport and use? Given that my scope has just done 200 miles strapped into the back seat of my car moving at 90 mph I am expecting to have to make reasonably significant corrections - would you expect similar?

Sorry to bang on - what are your thoughts on an EQ6 as a new mount?  Is it sufficient or should I think about a CGEM.  I'm reluctant to go for the latter as I really like using EQMOD.

Cheers

Simon

The 10" LX200 was my first proper scope when I got back into astronomy after many years break. Loved it - then hated it.   Optically these older versions are some of the best Meade ever made, mechanically and electrically there were 'issues' (most to do with the fork mount, but also the focusing and mirror cell arrangement), So mine had a lot of mods done to it over the years to correct some of the shortcommings as I saw them.

The transport bolt hole can be found to the right hand side near the focus knob, it is used (as the name suggests) to hold the mirror in place during shipping. People have used this to stabilise the mirror during actual observing/imaging sessions either by using a spring-loaded rod or simply locking the mirror and using an accessory focuser. Search the net for MAPUG and Transport Bolt and you should find more info. My mod was a bit more extensive but it allowed the mirror to move in a more controled way yet completely eliminated unwanted mirror movements. I also fitted a fan to the rear cell to help speed up cool-down times, and also made counter-balance weight systems and accessory mounting hardware for it.

The problem of vignetting cannot be addressed by fitting a different FR (I believe anyway), the issue is the narrow bore of the baffle tube which places a limit on the diameter of the light cone. It's not normally a problem unless you're using the largest sensors - FF etc., but just how big you can go I'm not sure, vignetting will be progressive and can be corrected with flats to a degree.

Once you get used to collimating it then the process is both fast and simple. I did find the need to design some replacement knobs so I could observe the effects of adjustments whilst  looking through the eyepiece at the same time. Bob's Knobs nicked the idea a couple years later and started selling them   I've transported my own scope over 15miles of very rough roads and it hasn't needed adjusting, but it's still worth checking at the start of every session anyway, if the seeing is bad you won't be able to make accurate adjustments because of poor star images - but then if the seeing is that bad then tweaking collimation back to perfect would gain you nothing anyway

I've never used the EQ6 variants but others say they are substantial mounts and the 10" should be well within their load capacity. I use a G11 which is fine provided the scope is well balanced.

ChrisH

[Apostate]

Thanks Chris

The MAPUG resource is a goldmine - thank you!

I think I'll put one of these in the back of the scope until a crayford is sourced and the mirror brought all the way back and locked.  Is this similar to the device you mentioned?

Looks as though I'll have to do some research on SCT baffle tubes and light cones.  I did think that the larger OTA would have a proportionately larger baffle tube and this might mitigate the clipping somewhat.  The MPCC is a coma corrector that sits in place of the 2" dslr adapter, screwed into the t-ring.  It is supposed to help correct the coma found on the edges of images produced by fast newts the cause of which also causes vignette - I figured that the vignette that appears when a focal reducer is used is caused by taking liberties with the light and bending it too far - thus, I figured, a coma corrector might put it back on the 'straight and narrow' for when it hits the chip.  If it is caused by physical obstruction by the baffle tube then.. well, a good way to acquire flats is going to be necessary..

I am, as ever, ahead of myself.  I'll get it mounted properly first.

Thank you very much for your advice.

Simon