inFINNity Deck

I have adapted an ADM clamp and dovetail to do those adjustments. It works really well, adjusting the scopes does not take more than 10 minutes. For images see figures 4 and 5 at the bottom of my C11 web-page: http://www.dehilster.info/astronomy/celestron_c11_xlt_edgehd.php Nicolàs

Please note that there are two type of RASAs (old and new model), so yours may differ from the drawing. Nicolàs

Hi Tich, Celestron does send parts and does do repairs (and they normally are quite communicative). Last year I received new vent-covers for my 11" EdgeHD SCT and later on I shipped the SCT to them to have mirror-flop repaired. That, however, turned out to become a huge disappointment as I explain in this article on a Dutch forum (it translates well when opened with Chrome). They do not disclose any technical information, not even regarding the repair, but especially their final remark ("I am sorry about the issues you experienced") after I found out that nothing had changed (apart from a big hole in my pocket) I found rather disappointing. Nicolàs

Hi James, indeed, that is correct, as very well explained by David at the second page of that thread: This week I received my photographic ronchi-eyepiece and last night I put it to the test using my 11" EdgeHD SCT. On that SCT I have a MoonLite focuser, so I was wondering what the best combination of mirror and focus setting would be. Last year I made a contraption that allows me to do afocal imaging using a ZWO ASI290MC and it appeared to function equally well on the ronchi eyepiece. The ASI290MC was equipped with ZWO's CCTV-type lens and focused at infinity. Then the mirror and focuser were moved until I got a ronchi pattern. Seeing was terrible and as below video shows, it was far from easy getting proper results. During the recording I played with both the mirror and MoonLite focuser, so the grating goes in and out of focus and even the SCT's mirror-shift can be seen. Clearly it would be beneficial to put the SCT in front of my collimator to do this test, but that means I have to take it of my rig. The video plays at 3 x actual speed. Nicolàs ronchi.avi

Yes, that can, see Nicolàs

I was surprised Astronomy.net managed to solve the original image with all that annotation and hand-drawn circles! 🙂 Nicolàs

According to Astrometry.net: Size: 44.2 x 29.4 arcmin Radius: 0.442 deg Pixel scale: 0.484 arcsec/pixel In fact the pixel size is (44.2 x 60)/5472 = 0.484649 "/px The sensor has a pixel size of 6.55micron, so the focal length would then be (6.55 x 206.3) / 0.484649 = 2788.1mm Of course I could be wrong... Nicolàs

I had this same 'issue' with my SkyWatcher 300PDS, so after collimation the secondary looked rotated. It was caused by the focuser not looking towards the centre of the tube, but being at an angle with it (as seen from the secondary mirror). The PDS focuser has push-pull adjustment screws that allows you to tilt it: The whole problem with a skewed focuser is, that the central ray will not hit the secondary at the centre, but in order to get it at the centre of the primary, the secondary needs to be tilted. So although collimation looks good, it is not as the central ray as not parallel to the tube and thus not perpendicular to the optics. The difference are however small and perhaps not even noticeable. This is what the focuser looked like after I had adjusted it for tilt, the adjustment is obvious (from the factory it was parallel): I adjusted the focuser using a laser collimator. When looking from the front it is a matter of aligning the spider with the reflected image of the spider and then trying to split the laser beam on the secondary with it (this may be an iterative process, depending on the collimation error in the primary mirror). After this was done the rest of collimation was done as usual and the secondary came in line with the focuser. HTH Nicolàs

Hi Nigella, I use that LesveDomeNet system that Steve suggested for my dome, and it works like a charm! Used almost the same motor, but using a chain and sprocket to drive the 450kg dome. On my website you will find how I installed it, including diagrams for providing enough power in a safe way (although I think your dome will need less power, being lighter than mine). Nicolàs

Hi HydrogenBadger, the diagram I gave was for this flattener, so please ignore it and use the following info: Nicolàs

Below diagram shows you how much space there should be between the flattener (assuming it is a Flattener 6 for GT71) and the chip. Your camera has 6.5mm from its front surface to the chip. So for the GT71 you need 65.82-6.5 = 59.32mm of spacers between the rear surface of the flattener and the front surface of the camera. Nicolàs

Strange, in my mailbox I see that you wrote: So apparently there is 120mm of 'material' missing between scope and camera. The flattener is 11mm, add to this 50-60 spacers you have, makes 61-71mm, so still 49-59mm needed. I have no idea how much the focuser extends, but if that is 60mm or more it should be fine to get things into focus. Nicolàs

Hi HydrogenBadger, Your scope has a 420mm focal length, so the CMOS surface should be around 420mm behind the centre of the objective, which can easily be measured with a tape measure. HTH, Nicolàs

It does make sense, although I am not sure if I can help. Only thing I can say is, when my SGP reports a 'external disconnect of dome detected' it is because my LesveDomeNet installation (that controls the dome motor) detects no movement while the motor is powered. This is a built-in safety feature that avoids the motor to run with the gear only half in lock. If it would continue running, it would damage the chain it runs in. The stalled dome is detected by LesveDomeNet and reported through the ASCOM driver to SGP, causing this external disconnect message. Of course there is bound to be some backlash in the dome-drive system, so that may cause a false detection. So in your case you could check whether such a safety feature is present in the dome controller and, if so, if it can be set-up to respond differently allowing longer periods of none-responsiveness. HTH Nicolàs

Dear Merlin100, when visual observing one has to be patient. Seeing is constantly changing and one has to wait for those short moments when it is at its best. Yesterday morning at around 3-4 am I was observing Mars with my C11 EdgeHD and a TeleVue Panoptic 41mm eyepiece. During moments of good seeing I could clearly see the icecap despite this low magnification of 68x. I then swapped the eyepiece for a 2x PowerMate and ZWO ASI290MC and ADC and shot the following image. Nicolàs

ok, thanks, good to know that not all ASI178MM suffer from this. Nicolàs

I used that video to clean my C11 EdgeHD and it is quite easy. Baader advices to use colour- and odourless Kleenex tissues, which I did use, worked like a charm. Make sure your workspace is properly prepared, so that you know where each piece (screws, retaining ring, corrector plate, etc.) is going to once taken from the OTA (and where all your materials are). A small sturdy table helps for cleaning the corrector both sides, I used a large square flight case for this. Finally, and perhaps most important: take your time, do not start this job an hour before lunch, dinner or any other appointment. Mind you that a broken corrector plate cannot be replaced! Good luck! Nicolàs

I thought that that plate only was to avoid Newton rings? What I was referring to are these horizontal lines every other row of the image raster. Nicolàs

Nigella, you are using the ASI178MM for your solar images and all seems just perfect. A Dutch amateur uses the same camera and gets horizontal banding, see below one of his images (I enlarged it by 400%, so every 4x4 pixels represents 1 pixel in the original). On the net I found several posts on a variety of fora that do mention these artefacts. Did you encounter them and, if so, how did you get rid of it? Thanks! Nicolàs

Hi Adam, I have a domed observatory with a side-by-side set-up myself. Common issues are the following: - measurements taken using the wrong reference (centre base of mount vs. intersection RA/DEC axis): Some software (like MountWizzard) knows the offset to the intersection of the RA/DEC axis for a number of mounts and require the centre of the base from which the RA/DEC intersection is calculated. - dome radius vs. diameter: some software use the former, other the latter. Some ask for the latter, but actually need the former (e.g. SGP). - accuracy set too wide: some drivers like LesveDome allow to set the accuracy with which the dome should be slewed. If this is set too high, the dome may not slew correct. Setting it too low, may cause the dome to jitter between positions. - Lateral offset of imaging scope: as far as I know only MountWizzard can handle the lateral offset for an imaging scope, all others assume the scope to be mounted at the centre of the mount. I have recently written an article for these calculations, which I hope will be published this month or next month in https://astronomytechnologytoday.com Nicolàs

Let me add one more of day before yesterday (night of 30 to 31 July). Processing done in the beta version of APP that now has a comet option. Imaged using SkyWatcher Esprit 150ED and ZWO ASI1600MM Cool Pro, 4 x 12s subs in LRGB, so 16 minutes of data. Stacked in APP without outlier rejection. Nicolàs

I would recommend to stay at least well above 1 second (2 seconds for non-Pro models). Not only for the effects described above, but also to avoid interlacing as a result of the flat panel's (laptop's screen) flicker rate. When short exposures are taken interference will occur between the exposure length and update rate of the flat panel, resulting in interlacing effects (horizontal bands) in the flats. The skewing due to low exposure times in non-Pro models will not be very obvious when doing single panel work or when using processing software that deals with uneven illuminated subs, but it is better to avoid. Nicolàs

Hi Adam, be careful when it comes to using short exposure times for ZWO ASI1600 cameras. Depending on the type of 1600 you have and the USB interface that is used (USB2 or USB3), there is a tipping point at which the camera used global shutter or rolling shutter. You may find the following thread of interest: https://www.astroforum.nl/forum/astrofotografie/beeldbewerking-methoden-en-technieken/1438084-daar-is-dat-lastige-onderwerp-weer-flats?p=1438404#post1438404 It is in Dutch, but opening it in Chrome should provide a decent translation. Summarizing, the Pro editions of the 1600 do not have a tipping point, but all the others (ZWO ASI1600, ZWO ASI1600 Cool, both the MM and MC models) do (2s at USB3 and 5s for USB2). The method used causes the flats to be skewed (darker on one side than on the other). You stated that you use a ASI1600 Pro, so you should be safe. Nicolàs

As promised, I hereby post an image of the tool I made to loosen and re-tighten the planetary gear. I have placed additional images and explanatory text on my web-site (figures 3, 4, 7 and 8). Nicolàs

The seeing is of course also very much depending on season, latitude and elevation. Were these factors in some way included in those calculations? Nicolàs