Fred_76

@spordniar is absolutely right ! The formula are the same, the one I give is just simplified 😉 However I found that using 30 pixels instead of 10-15 gives better results. Therefore the formula becomes : d' = 100 x p / F Where : d is the dithering in arcmin, to enter in the SAM console p is the pixel size, in µm F is the focal length in mm I do not agree on the statement of @vlaiv when he says : As the drift in DEC will always be in the same direction and at the same rate, it will generate a trail, responsible of walking noise pattern. It will not generate any "natural dither". To reduce the countereffect of the drift in DEC, when dithering on RA only, you have to dither a lot, so the 30 px instead of the 10-15 usual pixels that are commonly used when dithering in both directions. Note that the standby time between two photos will be affected by the dithering operation. As the Star Adventurer Mini can only move at x0-x1-x2 the sidereal speed, the duration in seconds of a dithering jump will be at max four times the arc.min set in the app. For exemple if you set 5 arc.min, the duration of a dithering will be 4x5=20 s (this is a max value as each dithering jump will be random between 0 and 20 s) + some seconds to stabilize, before the next photo starts.

Have you ever seen laser debayering ? That’s ongoing here (in French indeed): https://www.webastro.net/forums/topic/196977-debayering-capteur-au-laser/ Fred

Hi. I own an antic Vixen Polaris with its original MD-5 Quartz controller. Does anyone have an idea how I could add ST4 possibility to this controller ? There are only 3 buttons : Stop x2 x8 This idea is to link the Stop button to the RA- ST4 pin, and x2 button to the RA+ ST4 pin. Would this work if I just link the buttons like this, or do I need a more complex electronic mount (with optocouplers, resistors...). Clear sky Fred

Hi. I own an antic Vixen Polaris with the MD-5 Quartz controller. Does anyone have an idea how I could add ST4 possibility to this controller ? There are only 3 buttons : Stop x2 x8 This idea is to link the Stop button to the RA- ST4 pin, and x2 button to the RA+ ST4 pin. Would this work if I just link the buttons like this, or do I need a more complex electronic mount (with optocouplers, resistors...). Clear sky Fred

Hi Phil, I have the same issue as you. I am trying to add the dithering capability of any ST4 compatible mount (and the Astrotrac) automatically, without any computer, with some Arduino hardware. See here (subject ongoing, in french only) : https://www.webastro.net/forums/topic/192073-dithering-et-intervalomètre-autonome-en-arduino/ But DO YOU HAVE THE USER MANUAL of the Astrotrac TT320X-AG ? I can't find it and the previous owner of my mount can't find it... Fred

Tim from WO told me it was FPL-53, not FPL-51 on the ZS 80 FD Black & Gold edition I have. I don't know for the Red edition. FPL-53 is far more effective (Abbe number = 94.93) than FPL-51 Abbe number = 81.54). The higher Abbe number the better to reduce color dispersion and color aberration. The Abbe number of fluorite (CaF2) glass is about 95, just slightly above FPL-53.

Hi all, Here is a short movie demonstrating the slow motion of Venus in the sky. It was made during the transit of the planet through the Pleiades, from 500 photos (5 s exposure each) and a total duration of 1 hour 24 minutes. All comments welcome ! Fred

This trailing is due to periodic error. The SAM periodic error is big, about +/- 90" (or 180'' peak to peak). This is why you shall perfectly balance your equipment on the mount to reduce it a the minimum, and not use to long focal length or exposures. The SAM is not designed for focal lengths above 150 mm or exposures times above 60 s. Look a the internals here : https://www.webastro.net/forums/topic/181169-star-adventurer-mini-périodes-des-rouages/

Note that dithering is only available if you have updated the SAM firmware to version 3.10 or above. I took 10 pixels and arrived to that rule of the thumb: d' = 35 x p / F Where : d is the dithering in arcmin, to enter in the SAM console p is the pixel size, in µm F is the focal length in mm You cannot enter decimal numbers directly in the SAM console (at least in iOS). To do that, juste enter 0 and press Done. You will see 0.00 in the box. Then just edit the figures and don't delete the decimal separator ! I saved a profile for each lens/DSLR combination I use so that I don't need to calculate that again. Fred

Hi all, I proposed at Cloudynights a thread with some tricks to improve the accuracy of the Sky Watcher mini equatorial wedge that many of us use for their mini tracker. Here is the thread : https://www.cloudynights.com/topic/700024-skywatchers-small-equatorial-wedge-improvement-solution/ Those tricks are quite straightforward and greatly improve the wedge's behaviour. Fred

OK, nice insides, but could you give us more details than simple photos ? - number of teeth of each spur gear - diameter of spur gears - reference of the DC motor (if any) - reference of the gearbox (if any) or at least if you can unscrew its cap, a detailed photo of the internals - reference of all roller bearings of at least shaft diameter, external diameter, thickness and number of balls/cylinders All the best Fred

Did someone succeeded in measuring the gearbox ratio ?

No Wim, I sold all my astro equipment... here in Normandy, we have not enough good nights per year to shoot the deep sky, and I was quite frustrated to have such costly equiment standing by my garage. I had an AzEQ6 with a SW200/1000. The PEC was working correctly with EQMod and the 71t belt, with the period set to 478.7s. I never had the time to change to the 72t belt before I sold my mount, however mechanicaly speaking, this can only improve the PEC as it will compensate the defects of more mechanical elements.

Hi! It should have been better to replace the 71 tooth belt by a 72 tooth belt on the RA axis. The difference in length is minimal (2.5 mm) and the play in the motor's shaft position is enough to tension the belt. The big advantage is that with a 72 t belt, the motor pulley, worm gear pulley and belt are back in the same position every 3 turns of the worm gear instead of 71 turns with the 71t belt. It is then much easier to do a PEC : you just have to enter the period of the 72t belt x 2 (i.e. 1436 s). Here is a list of associated periods. AzEQ6 with 71t belt (original) - motor pulley (12t) : 119.7 s - belt (71t) : 708.1 s - worm gear pulley (48t) : 478.7 s (use this value for PEC but it will not correct belt errors) - combined pulleys and belt : 33 986.9 s AzEQ6 with 72 belt (modification) - motor pulley (12t) : 119.7 s - belt (72t) : 718.0 s - worm gear pulley (48t) : 478.7 s - combined pulleys and belt : 1 436.1 s (use this value for PEC and it will correct all errors of the belt drive) Autoguiding with PEC "on" is possible with EQMod. Fred

Hi Gina, This is a working example of your idea