IanL

Inspired by this thread on the SolarChat forum, I built my own Solar Scintillation Seeing Monitor (SSSM). I've written up a detailed build guide here to help those less electronically inclined to build their own: http://www.blackwaterskies.co.uk/2017/06/diy-solar-scintillation-seeing-monitor-sssm/ What is an SSSM? It's a simple device designed by E. J. Seykora at the Department of Physics, East Carolina University which uses a photo diode, amplifier and an Arduino-type board to monitor solar seeing conditions. (Note: This device is not suitable for monitoring night-time seeing). Commercially built and supported models are made by Airylab in France and sold through various distributors at a cost of around £240 at the time of writing; the DIY version costs less than a tenth of this to make and is functionally identical as far as I can tell. Why would you want to monitor solar seeing conditions? Apart from scientific interest and perhaps comparing the quality of seeing conditions between locations, the main reason is to use Joachim Stehle's free FireCapture plugin (here). The plugin will continuously monitor seeing and automatically start capturing images/video when they exceed a user-defined quality threshold. This means you can set up your solar imaging rig and leave it to its own devices rather than having to fill up your hard disk with gigabytes of videos that you then have to sort through manually later. I have made a couple of small improvements in my version of the build, specifically refactoring the Arduino sketch to make it more readable and more modular, plus I've added support for graphical display of seeing quality over time by adding a cheap OLED display and supporting code. (OLED modules can be had for less than £5.00 on eBay). Hopefully you'll find this an interesting project for the summer months!

There is a drawing with measurements on the Baader site here:http://www.baader-planetarium.de/sektion/s35/s35.htm There is no drawing for the SW adaptor though so you need to add a bit more. The Steeltack plus tube adaptor is a bit longer than the stock SW. I will try to measure tomorrow and report back. So you need to rack the tube in a bit more than with the stock focuser. There was still plenty of travel left though. What will you be using on the focuser?

We're now official, this thread has been linked to on the Baader page for the Steeltracks: http://www.baader-planetarium.de/sektion/s35/s35.htm

Now they are officially released just a quick update. My schedule and the weather finally cooperated last Saturday so I have used the beast in anger at last. The results are good. Focus action is smooth as expected from the bench test, no problems with sag or slippage at all. All in all a very worthwhile upgrade.

On most Crayfords the lock screw either bears directly on the draw tube or perhaps on the rear of the drive shaft centre 'bearing' (which on the SW focuser is a block with v shaped cut and Teflon pad in which the shaft sits if I recall), thus increasing the friction between the shaft and flat on the draw tube. Either way there is a definite tendency to deflect the tube a bit or a lot. On the Baader the position of the lock screw is offset well to the side of the centre line of the focus tube, and it looks like it basically locks the shaft from rotating rather than trying to increase friction on the tube directly or indirectly. The really high friction between the drive shaft and the steel rail attached to the bottom of the draw tube stops the tube from slipping when the shaft can't rotate. I guess the mechanism must be similar to the Moonlite shaft brake; there is no deflection of the tube as you don't need to tighten the lock screw much, plus the roller bearings run on two flats at the 10 and 2 o'clock positions on top of the tube. They look much better engineered than the two tiny bearings in the SW focuser so there is less opportunity for the tube to move out of line. I assume any bearings in the drive assembly are similarly high grade. With regard to the drive shaft being driven by the tube when unlocked, there is no problem at 45 degrees with my approximately 2Kg of gear attached. On the bench with the 5Kg weight sat on top of the tube, the drive shaft and knobs ran freely when released, so I'd assume with a really heavy setup at high elevations you would need the focus lock to avoid slippage. You certainly can part apply it when near focus - I haven't seen the internals but from the feel of turning the knobs when it is part tightened there's no grinding feel or anything to suggest you shouldn't. The marketing blurb says you can increase the bearing pre-load if needed for a heavy setup, but no idea which screws to adjust to achieve that. Of course if you were using a stepper motor drive and belt the motor should hold focus without locking. If you thought the old Steeltrack was a good product, I don't think there would be any concerns with the new one.

Well if that is the case I had better buy a lottery ticket this week then!

OK thanks for clearing that one up.

I can't say whether a Moonlite would be better, and perhaps I'm overstating the niggles but I did want the review to be honest rather than just focusing (!) on the good points. - The lack of documentation is not a big deal, just seems to me it wouldn't be hard to supply a basic set of instructions as a PDF on their web-site. - The Moonlites don't look to be rotatable as far as I can see, which would be a big downside for me as I can never get the framing right in my head when setting up, so the mechanism on the Baader is still a plus in my book. It locks more than sufficiently well for imaging purposes, it is just a bit awkward keeping the right angle as you're reaching the final turn of the locking ring. With the Moonlite you'd be forced to rotate the camera in the draw tube as far as I can see (?), and if you didn't like the Baader mechanism you can do the same thing. - Changing the adaptor at the camera/eyepiece end wasn't great, but with the kit in place I can't see any shifting around. You could just go with the factory supplied compression ring and avoid the whole problem - again it looks similar to the Moonlite's one. -What I will say is that having used a couple of low-end Crayfords now, the new Baader mechanism is excellent by comparison. It seems to combine unbreakable friction with uncanny smoothness. I keep going to rack the thing in and out just for the feel of it. I don't know how the Moonlite mechanism stacks up by comparison, but I cannot see how it would beat the Baader. At the end of the day you pay your money and go with what you prefer. There isn't a huge difference in price and I guess this is one of those occasions where getting hands-on with both would be the only real way to decide.

Not yet, if it ever stops raining here I will try to get outside and give it a proper test. I can't see that there will be any significant issue to be honest as the whole thing is very well put together. I think you will be pleased.

Sorry I couldn't buy from you guys as well but I guessed they would be super popular and didn't want to miss my chance after a long wait. Looks like TS are now on back-order too so I don't think there will be any shortage of orders when they do turn up here.

After a long wait for the new version of the Steeltrack focuser to become available, I have finally obtained one from Teleskop-Express (Germany). I needed one to replace the stock focuser on my Skywatcher 80ED Pro. The old focuser proved serviceable when used with my lightweight DSLR, but it is not up to the job for my pre-loved Atik EFW2, SX CCD plus the Skywatcher 0.85x reducer. Despite trying to improve it by tightening up the mechanism and grinding flat the focuser tube bearing surface, it would not lift the new gear consistently or reliably. The Steeltrack looked like a good replacement but was no longer being made, and I didn't think a cheap and cheerful ED80 really warranted a new Moonlite or Feathertouch (I doubt my dear wife would have either). Fortunately the new version of the Steeltrack has just been released after a long wait. I purchased: 1 x Baader Diamond Steeltrack-RT Focuser (part number BA2957210) 1 x Baader universal Adapter for TS ACUR2 and Steeltrack Refractor (part number BA2957085) 1 x Baader 2" Clicklock Clamp S58 (part number BA2956258) Total Cost 457.90 Euros including UPS shipping to the UK (£334 quid or thereabouts). The universal adaptor contains a number of parts that can be used to fit to a variety of refractors, including the ED80, but bear in mind there are other adaptors available for some tubes so I guess it should be called the "universal-ish adaptor". The Clicklock clamp replaces the standard three-point compression ring fitting on the focus draw tube. Since I already use a (different) Clicklock and like it very much, I decided to go down that route, though the standard adaptor looks perfectly serviceable. Fitting was relatively straightforward, just a question of assembling the adaptors and focuser, undoing three screws at the back of the ED80, sliding out the stock focuser and sliding in the new one, and re-inserting the existing screws. There were a few niggles, which I'll cover below. The Good Things - Overall, the build of the focuser is very solid and well engineered. Surfaces are well finished, anodising is good and there are lots of screws holding everything together. Holding the stock SW focuser and the Baader in each hand, it is clear they are in different leagues engineering-wise. - The focus action is incredibly smooth, both on the normal and the 10:1 fine control knobs. There is no slipping, jerking or friction apparent in the mechanism. - The lifting power is claimed to be 6Kg. I tried the focuser with a 5Kg counterweight sat on top of the draw tube on the bench and it lifted and lowered it perfectly, no adjustment needed out of the box so I think the claim is justified. - The lock screw mechanism is definitely required to hold focus with heavy loads. The Crayford drive mechanism doesn't slip at all, but a heavy weight pulling or pushing on the tube will quite happily drive the focus knobs. (Oddly enough the old SW focuser wins here, as stiction in the mechanism tends to hold things in place when you release the focus knob). The lock screw appears to bear on the drive shaft rather than on the tube or somewhere else. As far as I can see this means the image won't shift or tilt when locking, but that remains to be seen in practice. Certainly it only requires a small amount of pressure to lock the mechanism solidly with a normal load applied. In any event, focusing would likely require both hands if pointing high up, one to hold the focus knob still and one to tighten the lock. - There is a ruler scale on the draw tube; useful as I suspect this focuser will be used a lot by imagers looking to upgrade inferior kit. - The fine-focus knob has both a chunky knurled section for hand operation, plus a section profiled to take a small drive belt for the optional Steeldrive focus motor. (I plan to make a DIY focus drive, but it is good that one doesn't have to remove the existing knobs to connect a belt). - The focuser body is rotatable, again very handy for imaging as one generally doesn't want to mess with the camera and draw tube adaptor in the dark for fear of accidents. - Allegedly the focus mechanism can be removed and reversed if you want the fine control knob on the other side of the tube. The Less Good Things - There is no manual or other documentation supplied or available on-line (even in German), other than marketing materials. It took a bit of guesswork to figure out which parts I needed in the adaptor for my set-up - wasn't too hard to figure out but why not explain it? - Nor are there any instructions on reversing the focus mechanism for left-hand use or increasing the tension. Not that either was necessary in my case, but the marketing blurb says you can do it. There are a plethora of screws on the underside and top of the focuser, and I wouldn't like to have to guess which does what. - There is no finder shoe. Apparently a separate kit is available to fix a finder, but bear that in mind if you are a visual observer (doesn't matter to me as an imager). - The focuser rotation mechanism works by loosening the large locking ring at the back of the OTA. This has three knobs a bit like a capstan or ship's wheel so it is pretty easy to undo and tighten as needed. The problem is that the locking relies on friction between anodised surfaces inside the locking ring and on the screw adaptor that fixes it to the focuser body. It is a bit of a performance to hold the focuser body still at the desired angle whilst locking it, as there is a tendency for the body to rotate as you reach maximum tightness. It is also possible to rotate the body with moderate force whilst locked - probably not an issue in practice but might be worth investigating whether a thin ring of friction material between the mating surfaces would help. The Bad Things - The "S58 dovetail clamping mechanism" for holding different adaptors on the draw tube turns out to be a ring of six tiny hex-head, cone tip grub screws. These fit behind a very small circular dovetail ring. Changing the standard three-point clamp for the Clicklock was a horrible task (as is any job involving tiny hex-head screws in my view). These tiny screws have a tendency to round out the head at the slightest provocation, even when using high-quality keys, and the threads on both the screws and the focuser body seemed to be poor compared to the rest of the piece. I'm not super-happy with the fit - it doesn't look like the clamp has any chance of falling out but there is a tiny amount of play left despite my best efforts. If I was more mechanically inclined, I'd be tempted to tap the holes out to M3 and use some bigger grub screws. The threads on the existing ones appear to have a major diameter of 2.3mm which is not a common size as far as I can see, so don't lose any down the back of the sofa (they might be M2.5 since the hex head was 1.3mm so maybe my calipers are a bit off, but hard to tell really). - I'd have preferred to screw-fit my SW 0.85 reducer to the draw tube, but there doesn't appear to be an adaptor for that available (which is a bit of an oversight given the market this focuser is aimed at). Overall This is definitely a major step-up from the stock SW focuser on the 80ED. Time will tell whether it works in practice but first impressions are generally good.

Ben, 1. I didn't say the pixels are 4.7µm2, I actually said the sensor has 4.7µm square pixels, meaning the pixels are square (not rectangular as some older cameras have) and 4.7µm on a side. We are using linear measurements to determine the pixel scale, not areas, so if you've calculated the area of one pixel you need to take the square root to determine the length of one side. Sorry if the bad choice of words caused any confusion, but too late to go back and edit the post now. 2. I've used the effective pixel count since that is readily available to a beginner from images. It is definitely more accurate to use the total pixel count and sensor area if you have that data available, but at the time I wrote the post I didn't. Where I can get a data sheet for a sensor I will use it as the source for information in my imaging toolbox, but often one has to rely on incomplete information from supplier marketing materials and they may quote total or effective pixels (and indeed in some sensors you can have slightly fewer or more effective pixels depending on how you configure the electronics). It's pretty immaterial in this context, the difference between using 4.7 (actually 4.69)µm and 4.63µm in my example results in a pixel scale of 1.88 arc seconds per pixel vs 1.87 arc seconds per pixel, a difference of 0.0243 arc seconds per pixel if you want the gory details without rounding up/down. The difference matters more at longer focal lengths. If you want to get really down in to the weeds, you need to know the number of active rows and columns on the sensor, not just the difference in the total vs. active megapixels. The inactive pixels will not be an equal number of rows/columns in most cases, and also there are more pixels in a row that a column on a typical rectangular sensor.

Sounds very much like there is no star in the image and so PHD will just bes stretching the noise to produce the grainy white out you see. Things to check: - Focus. Start with the moon as it will be obvious when it is the frame and then get focus. - Framing. Next try a bright star or planet. You will still get a white or black snowstorm until you have a star in the frame. Bear in mind the guide scope may not be pointing at the same spot as the main one. - Gain/brightness. Test this on the moon too in order to get in a sensible range for night time use. - Exposure length. I don't know what the max length is for your webcam so do some testing. Bear in mind that a long exposure in PHD may still only end up in a short one at the camera if the hardware or driver don't support long ones.

I have only had a small amount of experience with an OAG and not a lot of luck so any advice from me comes with a health warning. What occurs to me is: - A small pixel scale might lead to a lower SNR on the guide star, but this is likely to be offset to some extent by the bigger aperture of the main scope gathering more light. Nonetheless finding a guide star with the OAG may need you to pick a relatively faint one. So OAGs tend to need longer guide exposures, 7 seconds plus is not uncommon vs. 1 or 2 seconds for a guide scope. - That in turn means you need a mount that tracks better between guide corrections. So polar alignment becomes important, as does a lower periodic error. Using PEC can make a big difference but ultimately you will need a mount with good mechanicals, especially at longer focal lengths. - As for PHD settings, calibration should take care of most issues automatically provided you adjust the calibration step size. PHD 2 has a calculator to help work this out. You might want to increase the Min Motion setting if you are oversampling the seeing to avoid chasing it, but I suspect the longer exposures will average that away. - The main challenge is the gap between guiding commands due to the long exposure. I think you would want to use Resist Switch in declination, or guide in one direction only if you have slight drift, as backlash and constant changes of direction will be harder to control with long gaps. In RA I'd be inclined to use at least 100% of the correction for RA Aggressiveness and reduce the amount of hysteresis so that you are relying more on the current error than error from many seconds ago. From there tweak based on the guide graph, again PHD 2 has more options and tools for this but I am not sure I entirely trust it yet. Others may have some better ideas based on more experience.

You need a guide camera with a suitable driver for use with PHD. The new version of PHD (http://openphdguiding.org/) supports the following cameras (taken from the manual): Camera SelectionThe Camera drop-down list shows all the camera types currently supported by PHD2. With the exception of ASCOM-compatible cameras, the camera drivers are bundled with PHD2 and will reside on your system after the PHD2installation. ASCOM-compatible camera drivers are available from the ASCOM web site or from the camera manufacturer, and the drop-down list will show only those ASCOM cameras that are already installed on your system, if any. The list of supported cameras at the time of writing is shown below - but users should consult web resources to see updates (e.g. Stark Labs) Supported cameras, December 2013: ASCOM v5/6 compliant cameras (Windows)Atik 16 series, 3xx, 4xx, 4000, 11000 (Windows)CCD-Labs Q-Guider (Windows)DCAM compliant Firewire (OS X)Fishcamp Starfish (Windows and OS X)Meade DSI series: I-III, color and Pro (Windows and OS X)MagZero MZ-5 (Windows)Orion StarShoot DSCI (Windows)Orion Starshoot Autoguider (Windows)Orion Starshoot Planetary Imager and Autoguider (Windows)Opticstar PL-130 / PL-130C (Windows)SAC4-2 (Windows)SBIG (Windows and OS X, but see Help for details)Starlight Xpress SXF / SXVF / Lodestar (Windows and OS X)The Imaging Source (Windows and if Firewire, OS X)Webcams (short and long-exposure - parallel port, serial port or LXUSB, Windows).

Well done, take the rest of the week off!