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Thanks for that info. I did look at usb focus as an option, but I can't justify the cost at the moment. My dealer has kit listed at around 180e without holding bracket, brackets are around 85e and additional motor is around 90e That would total to about 570e with VAT and customs fees - pretty steep. I believe that I can motorize both focusers for quarter of that price if I choose DIY route.

I just realized that I will not be as straight forward as I thought. Although both focusers are of the same name - TS 2.5" - they differ in fine focus knob and travel per turn. On RC I believe that fine focus knob will have to be replaced with either pulley or coupling, depending on mounting position (below or to the side). On TS80 APO fine focus knob already has proper grooves that I can use to put belt on. I was hoping to leave focusers "intact" and just mount motors to them, but it appears that I will need to mod at least RC focuser. I've found good "summary" resource on this one that helped me understand differences between mounting options: https://astrojolo.com/astrolink-4-0-mini/focusing-stepper-motor-solutions/ According to that page, coupling to fine focusing shaft is pretty good option. Did some calculations and it looks like there will be enough resolution with 200 step motor and fine focus reduction to be able to go as low as F/4 - which is enough for my needs. Now I just need to find where to source pulleys, belts, couplings (I can do it online, but would rather like to inspect items for suitability prior to purchase).

This is pretty much how I thought it will look like - I'm also thinking about Nema 14 motors in combination with Arduino nano and a driver. Found where to source most of the items, just need to see about the belt and pulley, and to figure out a bracket for attaching motors (that will also probably be DIY out of piece of metal sheet - little drilling and bending). Found this open source project: https://sourceforge.net/projects/arduinofocuscontrollerpro/

Thanks! Do you mind if I ask couple more questions since you seem to have similar setup? Since there is no position encoder, I presume that it will be ok to use position marks on focuser tube? Focusers have mm markings on them, and for instance, on RC in certain setup (I will probably have different setups depending on use of focal reducers and components in imaging train) focus position is at about 20mm - so I can set range of motor focuser to be between 10mm and 30mm (with appropriate number of steps) - so each time I want to use different setup, I position focuser on 10mm (or equivalent "start" position) before powering everything up and tell it that it is at step 0, right? How does above relate to focuser calibration in SGP? How often do I need to create full V curve? If there is position change (either due to me fiddling around, or mentioned slip / drift) will SGP cope with that (it should since V curve is just approximation it should find right focus position by half flux radius anyway)?

I think I pretty much made up my mind on this one, but would like to hear any pros and cons from people using these. I'll probably go for DIY solution since I have two scopes with same focusers (2.5" R&P TS), and that will help me "split" costs - I'll have two steppers - one on each focuser and single control box (probably attached to mount). I'm not entirely sure what my concern is, I can only see benefits of using ASCOM controlled, motorized focuser - coupled with SGPro. I just want it to be minimal hassle to connect and use. Actually here are my concerns about this: 1. I'm feeling that I'm already approaching weight limit for "stuff" on focuser side for my RC8" - last imaging session I noticed change in outer field astigmatism as scope moved around the sky and mirror was in different positions. It was very slight effect but it points to one of these things: mirror is coupled to focuser so total weight on focuser is causing slight mirror tilt at different positions, or weight of all the items on focuser creates "sag" somewhere along the way (threaded connection to focuser, quite a bit of spacers, extension tubes, so something might have some flex in it), or hopefully, collimation locking screws are a bit loose (did not check it, but will do first thing), so tightening up those will help. Stepper+bracket can add up to 300-400g on focuser side of things. 2. DIY design that I looked mentions temperature compensated design - I don't get this one, nor understand if I need it at all. My view is that I can set up SGP to do refocus periodically (like every half hour, or one hour) and I don't need to monitor temperature and refocus on ambient temperature change. Or is that better approach? 3. Since I don't want to mod focusers too much - I plan on using belt system coupled to 1:10 knob. Somewhere I read that this is not the best approach due to wear&tear of micro focusing system - but this approach allows me to use full steps (no need for microsteps to achieve needed resolution), and it does not require modification of focuser - I just attach bracket with motor and put belt on. This is related to my next concern 4. Both focusers are rack and pinion, and have lock screw that I usually tighten after finding good focus position. With motor focuser I presume that I need to leave this lock screw unscrewed. Will motor be able to "hold" position and focuser from changing focus / slipping (although it is R&P and should not slip but rather "unwind" under load) if I couple motor to micro focusing knob (I guess that can slip due to design)? a penny for your thoughts?

Just had a look, if your 70mm Quad is Altair Astro one, with ASI1600 you should have pin point stars across the whole field. They have spot diagram on their product page and it shows that spot diagram is less than airy disk even at 15mm distance from center - ASI1600 has diagonal of about 23mm so center to corner is less than 12mm. If there is dedicated tilt adjuster - it is there for a reason. Elongated stars in one corner or at one edge mean just that - tilted sensor. Above CCD inspector profile also suggests tilted sensor - just tilt your head to the right when looking at it and you will get much more acceptable looking field. According to description, there is tilt mechanism: "The Starwave 70 EDQ-R Quad APO is intended for astro photography and the focuser terminates in an M48 Male threaded rotator plate with locking thumbscrew. All screws are teflon tipped and grip on a flange for accuracy. The rotator plate includes a "push-pull" tilt adjustment system to enable you to square up the image sensor to the focal plane. " You should try adjusting tilt until you get symmetric looking graph in CCD inspector as a start and then look into any further issues (if there is any left).

Two things come to mind that can cause this: 1. Being quad, or having front lens, and integrated dedicated flattener - just means that flattener is matched optically to front lens, at a correct distance - so you are right, when in focus you should also be at optimal distance for flattener. Question is are all elements in scope properly collimated? It could be that rear element is slightly tilted or something. Does manual mention collimation or adjustment of any kind for this? Refractors ought to be factory collimated and very rarely need additional adjustments, but sometimes they do (for refractors, often that adjustment needs to be performed by skilled individual rather than "general public", unlike collimating newtonian or other mirrored systems). 2. Sensor tilt. Is focuser adjustable? Can you compensate for tilt in any way? It might be that you need separate tilt element to achieve sensor orthogonality to principal axis. No field flattener can provide "infinite" flat field, and usually there is technical spec on imaging circle, including sometimes just corrected field diameter and illuminated field diameter. More serious analysis and specification gives spot diagram over field and also illumination curve depending on distance from optical axis. Often if its just diameter of corrected field - it is more "acceptable" field rather than diffraction limited field, so you can start to see distortion near the edges of the field - something that spot diagram would clearly show. What is the size of sensor and does it match corrected field?

I've found this useful, and modified it slightly for my use (not using Bahtinov mask, but rather fwhm measurement in SharpCap): https://deepspaceplace.com/gso8rccollimate.php

I'll present my view on this topic, it might be a bit controversial, and it is not based on very big experience (although I've got some experience with RC scopes - I own larger brother of mentioned scope - RC8" F/8). I've done a sort of comparison of scopes in this class (6") and here is what I think: Let's take 5 representatives of different scope designs and compare, Newtonian, Refractor (we will limit ourselves to achromats due to price difference, and let's be honest, good APO triplet in 6" class will simply outclass all other designs on most comparison criteria), SCT, MCT and RC. RC vs Newtonian: - Newtonian will have an edge on planets, especially F/8 variant with small secondary obstruction. Such scope will be harder to mount (due to momentum arm, except for Dobsonian mount), but will have smaller FOV than RC (due to 1.25" focuser - because of small secondary). In faster ratios coma will be an issue. RC will also have larger light throughput - due to 99% dielectric coatings, regardless of larger CO - newtonians usually have 94% mirror coatings (enhanced versions) - you can go for special coatings like 97% hilux - then they will be better matched. - RC has better corrected field for AP so you can use pure mirror system without need for corrector. Corrector can be used to lower F/speed and further flatten already pretty flat field. Due to large illuminated circle - you can use 2" eyepieces and combined with focal reducer you can have wider views. - For planetary AP, due to processing and sharpening, central obstruction and loss of contrast have tiny impact, so these two will be pretty much matched (long focal length newtonian). - Price wise they are very close, newtonian being slightly ahead (cheaper). - Light baffling and stray light protection - win for RC. - Collimation ease - newtonian wins here. RC vs SCT - Shorter focal length and larger FOV for visual (f/9 vs f/10, 2" focuser). - Less prone to dew problems, and better thermal properties (open design) - Better photographic field (no coma, less curvature, ...) - Similar "format" for mounting, similar weight - SCT will have very slight edge on planets due to somewhat smaller CO, but light through put will be on RC side (again depends on mirror coatings, but SCT has additional corrector plate). - price +RC, -SCT RC vs MCT - just look at difference between SCT and MCT usually mentioned on internet (thermal stability, planetary performance, smaller FOV) - and apply to previous section (RC vs SCT) - all RC strengths will be emphasized, while planetary performance will lag. - price +RC, -MCT RC vs Refractor - it all comes down to fact that refractor - especially faster like F/8 or below will have very big CA issues - this means less contrast on planets, less contrast on DSO in spite of better ligth throughput - no CO at all. Photographic usability of such scope is limited to narrow band (you can do LRGB or OSC, but CA will have huge impact on final result). - Achromat will be heavier and harder to mount, and it will loose in price department. All in all, for that target budget, I think that RC is very overlooked option for good all around scope - both AP and visual. If you are worried about contrast loss on planets, have a look at this: This is simulated MTF of 8" RC vs 5" refractor (both ideal figure). MTF diagram is usually used to represent contrast loss - X axis represents spatial frequencies (or think in terms of large/small features, large features close to origin, small features to the right) and Y axis represents contrast loss (or attenutation in %, going from 0 at origin to 1 or 100% at top). What you don't usually see is such diagram comparing two different scopes - different aperture sizes and different CO characteristics. When you align spatial features axis (X axis) then you can see that smaller scope, although having "higher" contrast, actually looses on detail, and if you use scope with large aperture and CO with small magnifications (equivalent to what you would use with smaller unobstructed scope - you can actually have less contrast loss). Bottom line, RC might not perform as good on planets as other 6" options, however, it will probably be on par or even better than 4" apo if you keep your magnification the same (up to x200). Just to mention, those RCs seem to be optically very good instruments - I tested mine to system Strehl 0.94

It's a spacing issue, and a tilt issue. Spacing issue is going to be trial and error approach. It depends on size of chip, focal length of scope, focal ratio of scope, so it is not always "prescribed" distance. I've looked at some flattner (with reduction) specs, and they can vary greatly in "optimum" distance based on telescope type (F/ratio and focal length). Also some flatteners are designed to certain corrected field - so one can expect correction over given field, but if sensor is larger, outer parts will suffer and not be fully corrected. Procedure is simple - start at some distance and increase/decrease as long as you see improvement. Combine different length extension tubes and use distancing rings for fine adjustments (0.5-1mm range). First step in solving tilt issue is to go with threaded connection. One can probably fix major issues by using high quality / self centering standard connections (baader click lock and alike), but I think that best solution is threaded connection. Adjusting focuser for being square with lens is another thing that can be done (if there is some play in focuser, or if it can be collimated). As a last resort - there is tilt adapter that can be used (but it adds optical path, and probably best for permanent setups).

I do have one eyepiece of that type (not TS brand, I think it is SkyWatcher variant) and while it can be used for planetary observation, in my view they are poor performers. Mine has a lot of scatter and it is not sharp on axis (as it should be, or as other designs are). From what I've read, BSTs should have a slight edge in sharpness over it. This was in F/6 scope. In comparison ES82 11 with barlow, although yielding higher magnification, simply gives much better view, especially sharpness wise.

Feeling adventurous? I can't find any reviews of these, so maybe you can give it a test drive? Specs will not blow one's mind - 60 degrees AFOV, 12mm eye relief, but it is cheaper league, and description states: "...with an outstanding sharpness" (if one is inclined to believe those commercial descriptions ) https://www.teleskop-express.de/shop/product_info.php/info/p3828_TS-Optics-Flatfield-Eyepiece-FF-8-mm-with-60--apparent-field-of-view.html

I think you are right - I calculate exit pupil like this: EP FL / Scope FR, so in case of F/5 scope - 5mm eyepiece will give 1mm exit pupil. Or better remembered like this: Eyepiece with focal length equal to F/ratio of scope will give 1mm exit pupil, and around half of that will be max theoretical useful magnification (based on resolving alone - perfect optics).

On the other hand, if interested in orthos only, TS has nice selection of Kokusai Kohki Fujiyamas, no 8mm, but they have 6, 7, 9 and 12.5 (among others) - again prices seem to be right (around 100e, this time VAT included )

How about Vixen SLV line? I don't have personal experience with those, but from what I've read, performance is Ortho like, eye relief more than comfortable, and line happens to cover focal lengths that you might find useful (6, 9, 10, 12). Price is, I believe also within requirements (a bit more, but smack on 100euro without VAT )

If you are looking for a cheap upgrade to dual speed, have a look at this: https://www.teleskop-express.de/shop/product_info.php/info/p2625_1-10-micro-transmission-for-retrofitment-of-Crayford-focusers.html I've fitted it to my Skywatcher 8" dob, and it works great, quite a difference on fine focusing for planets.

I was just thinking about that, if Takahashi could do it with CN212, how hard can it be? But I would still prefer Cassegrain configuration to be with small secondary and long focal length - for planets.

All I can say from experience is that TS/GSO RC8" is worth the price. Someone mentioned focuser on this new Cas above, and it is the same unit as on RC 8" model - I ended up replacing mine. Although standard focuser (Monorail 2") delivered with scope is quite usable unit (for visual), there is serious drawback for its primary use (as astrograph) - it does not have threaded connection so tilt due to any mismatch in 2" interface is likely to happen. But if you just count a set of 8" F/8 RC mirrors - of quite good figure quality (I tested mine to be >=0.94 strehl) - at that price, I believe it is very worth it.

I know that one, and yes, I would like one of those CCF F/20 units at a price of GSO F/12 scope

I'm not sure about that one ... Looks like too much compromises. I would expect classical Cassegrain to be at least F/18, but it seems that GSO opted for F/12 for a number of reasons: 1. Reuse of tube and other components from existing RC model (both 6 and 8 inch) - F/18 or longer would require longer tube 2. Trying to make all rounder rather than specialist scope - bigger market share.

I believe worm period on HEQ5 is 638s (135 teeth so 10 minutes and 38s) while on EQ6 is smaller (180 teeth, larger worm ) - 479 seconds, or a second under 8 minutes. Recommended "dose" of PEC is at least 5-6 worm periods, so indeed 40 minutes is minimum for EQ6, but I would not go less than that - it is like regular stacking, more data, greater SNR and more precision in PEC curve.

I do also believe using PHD2 log and PecPrep to be more accurate. There are couple of video tutorials on PecPrep - worth looking at (they are short and easy to understand): If you follow next videos - you will get each part in a row.

I don't have permanent setup either, but for PEC you don't need to have it. PEC records imperfections in manufacturing of different components of drive train. It can't correct all imperfections - only those that are periodic in nature (like different gears not being perfect circles) - and only if they are harmonics of certain base period. EQMod PEC can only work with harmonics of base worm drive period. I've seen some question raised about viability of PEC when using different scopes on same mount. I think if one models PEC of mount - it should not matter what sort of scope you have on it - PEC needs to correct for drive error irrespective of the load. I use it with both small and large scope and it works. You can do PEC in early evening (not astro dark yet), or during full moon when you would not otherwise image. Do it only once and use it for subsequent sessions. You don't need to do it each time. I've done it just 3-4 times so far (after fiddling with mount - belt mod or regreasing / changing bearings). I need to do it now once more since I changed my laptop and lost PEC file (I actually saved file but sync was lost because of fresh EQMod install). You can even do it when there is high level clouds - as long as you select bright enough star and PHD2 is able to track it long enough (without star lost message). One more thing - best to select star near/on Equator - PE will have the largest amplitude there and most precise recording of it will be possible. PecPrep takes into account DEC of guide star (either read from log file, or you need to enter it manually, depending on guide app you are using - PHD2 its automatic). I'm a bit confused, what mount do you have? In your signature NEQ3 is listed. As far as I know, Rowan belt mod is available for HEQ5 and EQ6 models only. Other thing that you might consider is changing bearings on your mount (irrespective of model). They are pretty much standard - get high quality SKF and replace each bearing - it will also help smooth out mount tracking.

My experience is with EQMod (there has been some debate if PEC helps or whether guiding is fighting PEC, but for EQMod it seems that PEC helps quite a bit) and here is how I do it: I turn off guiding and use PHD2 to create log file (there is option in PHD2 to disable guide commands). I usually create about hour / hour and a half of log file. While doing that - at some point I press time stamp button in EQMod. EQMod auto PEC is also turned off. Next I load PHD2 log data into PecPrep and create PEC curve. After that I just tell EQMod to use that PEC curve and work "normally" from then on. I usually recreate PEC curve on significant change in system, or if sync is lost (HEQ5 does not have absolute encoders, and one must park each time after session to preserve mount position to PEC synchronization - if there is power failure or something and sync is lost - PEC curve needs to be generated again). In general PEC is meant to be recorded on "raw" mount data / motion - so don't have anything running that will disturb this - like guiding or whatever.

No, I have not heard about that one, but I'll have a look. I don't have a particular place for images (yet, I'm sort of working on it), but to tell you the truth I don't have much to show off. I started using RC last summer, and managed to get just a couple of images with it - most L channel (no NB or color taken with RC yet - I did combine color data from other scope on one of images but it did not turn out that great). Weather is just not cooperating for at least past 6 months (only one session, and that was short one). I post most of my images here in DSO imaging section, but to save you trouble, I'll link in ones taken with RC: http://serve.trimacka.net/astro/2017-07-18/ http://serve.trimacka.net/astro/2017-07-21/ http://serve.trimacka.net/astro/2017-08-27/ http://serve.trimacka.net/astro/2018-05-07/ Just open links and click on png. One of ngc7331 has a lum only (that is pure RC) and color one - mixed with data from another scope and another camera (TS80 F/6 apo and ASI178mcc - so not much color data and it is not that good). You can use search here on SGL for my posts in DSO imaging to see capture details for above images.