In February of this year, I decided to pair an ASI294MC one-shot color camera with a 31-year old 8” Meade LX200 “classic” Schmidt Cassegrain telescope and see if the combo could yield a semi-respectable image of a galaxy.  While I dream of someday shooting galaxies with a 9.25" Celestron EdgeHD, this charming little 8" LX200 Classic is the only long focal length telescope I own.  It's humbling to take to star parties, but it's light in weight and works really well with my Televue eyepieces for visual astronomy.    A couple of months ago, I removed it from its LX200 fork mount, plunged into the world of off-axis guiders, and been going further down that rabbit hole that galaxy fever brings.  I've asked my doctor about it and he told me there is no known cure for aperture fever.  Urghh. 

Since making these changes in late February,  I have managed to image 25 galaxies; some came easily and some with difficulty.  None of them are very good, but I am having a blast with this experiment.  Look for some images in the weeks ahead.  The three photos in this post, however, are to introduce you to: (A) the scope as it appears today, (B) the scope as it was in 2017, when I used it mostly for visual astronomy and occasionally for lunar or planetary imaging, and (C) a copy of the magazine add for Meade LX200's that attracted me to this scope back in 1991 (taken from Uncle Rod's Astroblog).

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DETAILS

Mount.  I removed the 8”  optical tube from the LX200 fork and mounted on ZWO AM5, which easily handles this lightweight OTA (18 lbs) with tracking errors of less than 0.7arc-seconds” on nights with good seeing conditions.  On full moonlit nights or "below average" seeing (windy or high-atmospheric moisture conditions), guiding is much worse, but usually less than 1.8° total RMA.  I did not mount the AM5 on the ZWO carbon fiber tripod (as nice as it is), but instead secured it on top of the original Meade LX200 tripod.    Years ago, I retrofitted the LX200 tripod with a triangular plywood shelf upon which I load 50 lbs of lead scuba diving weights.  This additional weight  greatly improves the tripod rigidity and I don't have to worry about the entire rig toppling over, even when wind gusts of 50 mph buffeted the scope and its Telegizmo cover.  I like to leave it set up in my back yard for weeks at a time.

Focal reducer/field flattener.  Over the years, I bought several f/6.3 focal reducer/field flatteners, none of which work all that well.  I will share posts of images made using gthe classic Celestron 0.63X reducer and the Meade (series 4000) reducer.  Although the Meade Series 4000 FR/FF says “made in China” on it, this one is apparently not a defective one, which many are eportedly to have been.  Images taken using both are still plagued with coma.  I have been slowly perfecting collimation, tilt and tracking errors, but the coma on the old LX200 is awful.  I upgraded to a Starizona Corrector IV (0.6x), a multi-ED lens corrector, which has made noticeable improvements in regions near the edge of the field.  But the Starizone provides virtually NO benefits in the middle of the image on a scope.  Considering that it is only 8" in diameter, I am not surprised.  Starizona correctors are known for being most useful for the 9.25" and larger SCTs.

Dew Control.  The blue Astrozap dew shield has an Orion dew controller adhered to the side of the OTA (Velcro patch), and 1” wide dew strap wrapped around the scope near the corrector plate where the dew shield attaches to the scope.  I run a dedicated 12V power supply to this big heater.  The main camera (ASI294MC Pro in this photo) also has the ZWO accessory dew heater that adheres to outside of the camera near the sensor chip.  The camera dew heater does not draw much 12V  power and in fact the power supply cable that ZWO provides with the dew heater splits the 12V coming from the ASIAir into two lines - one for the ASI294 camera and the other for the dew heater attached to the front face of the camera.   It is very humid and cold here in central Pennsylvania, so dew control is a serious matter,.  The dew shield alone is insufficient for the telescope and as for the camera, when I crank the cooling down to -10° or -20° on humid nights, water has condensed on the clear glass plate in front of the CMOS sensor if I don't have the dew heater turned on.  

Guider.  The second photo (B) shows the scope in 2017.  Between then and now, I replaced the Orion ST-80/Starshoot autoguider combination with a smaller, more elegant Stellarvue 50mm guide scope with helical focuser with an ASI120MM mini camera.  The quality of this Stellarvue guide scope blows me away.   This setup actually worked well at first, but I decided to make the shift to off-axis guiding so that guiding was at the resolution of the primary camera.  I started out using an 10-year old Orion OAG, which worked okay, but its prism size was tiny and it was clumsy and difficult to focus the guide camera or rotate the entire assembly.  A huge improvement was to upgrade to a new Celestron OAG and ASI174MM mini guide camera (I was using a ASI120MM mini with the Stellarvue guide scope). The Celestron OAG is heavy and bulky, but its prism is 4X as large as the old Orion OAG and I love the helical focuser it provides for the guide camera.  I use the James Lamb’s method of using an angle gage and Stellarium to plan out my OAG orientations before any imaging session.  Mr. Lamb’s method is working very well for me and I now find guide stars much more easily and consistently than ever before.  It’s still a challenge on full moons or poor seeing conditions, but using an OAG is no longer exasperating or discouraging..

Electronic Focuser.  In photo A, you may notice that I removed a beloved JMI Event Horizon focuser from the back of the LX200, thinking I needed to do so in order to achieve the critical back focus distance of 105mm for the Celestron or Meade focal reducers and ASI camera.  Thus, the imaging train shown in this photo consists of the following: (1) 6.3FR/FF, Celestron OAG with ASI174MM mini guide camera+22 mm spacer+ASI294MC Pro one-shot color camera.  I have also used my  ASI1600MM Pro mono camera with narrowband filters with this scope and they work fine.   Using ZWO’s EAF adapter for Celestron 8” and 10” SCts, which required I only file off a portion of the base to fit the raised lip on the back of the Meade LX200) I mounted it place of the manual focus knob.  This EAF set up does NOT work well for this scope.   There is  too much backlash and slop in the focusing assembly and the EAF software struggles to achieve a good parabolic curve in the graph of star size versus focuser position.    I have spent countless hours using the NINA and ASIAir autofocus routines to determine what the backlash, fine focus, and coarse focus settings should be.   Many evenings, I end up turning the EAF off completely,  because autofocus routines make it worse.  I am not giving up, but hopefully someone might be able to shed some light on whether it’s something I am doing wrong or that I should not expect an old SCT like this (prone to mirror flop too) to perform satisfactorily with an autofocus.

Update:  After purchasing the Starizona SCT Corrector IV focal reducer, I reinstalled the JMI focuser on the back of the SCT because the Starizona corrector is designed to fit directly into an 2" optical focuser (it does not screw onto the back of the OTA like the Celestron and Meade focal reducers).  Before re-attaching the JMI focuser to the back of the scope, I removed one of its focusing knobs, bolted the ZWO EAF and now it drives the JMI focuser, not the focusing knob on the Meade LX200.   This all went easier than expected and I was please to see that, after I rough focus using the old Meade focusing know, the ZWO EAF and JMI focuser yield pretty decent parabolic focus curves and achieve fine focus quicker and more consistently.  It is definitely not perfect, but much better.

Software.  About this time I also began playing around with Raspberry PIs micro-computers to operate the scope and set up planning sessions.  I have had good success with three PI variations: (1) StellarMate, (2) Astroberry and (3) ZWO ASIAir (original, Pro, and Plus models).  I enjoy using all three PI variations and appreciate their various strengths and differences.  I can operate the StellarMate and ASIAir using my smartphone and tablet.  I don’t have a microPC attached to my scope, but sometimes I connect everything to my laptop and sit outside for hours on end.  In those times, N.I.N.A. is my favorite software for imaging DSOs and SharpCap for imaging planets.  I also use FireCapture, but I like the user interface of SharpCap better.

Conclusions.  I have a long way to go in my experiment with this little old LX200 scope.  Thus far,  my images appear “soft” and require a ton of post processing to correct for optical problems, primarily coma.  I marvel at how others here on Astrobin can  take remarkably good images using classic 8” SCTs.  Most are using Celestron C8s, which is probably a better scope.  But there are some really good images taken with Meade LX200s.  And while this bad telescopes can sometimes drive me crazy, it is forcing me you learn the basics and exposing me to the challenges of using long focal length SCTs to image galaxies.