inFINNity Deck

Today their separation was only 9.5", already close enough to be captured with my C11/ZWO ASI174MM combination. As the forecast for tomorrow is not all too well, I imaged the two today: Nicolàs

If I checked out well in Stellarium, Saturn and Jupiter can be captured on one plate for three days this year with the combination of C11 with ZWO ASI174MM (below image was captured without Barlow, but with ADC). Tonight was the first chance, the two others oportunities will follow for the next two days. The weather was far from perfect: a lot of clouds, but fortunately also a few holes. Also the planets were at a quite low altitude: Saturn at 11° 13′, Jupiter at 11° 04′. Instead of using my usual 4 x 120s script, I set FireCapture up to make 30 second SER movies on demand. Then in between clouds (between 4:05 PM to 4:15 PM UTC) various recordings were made in LRGB, constantly manually adjusting the exposure to adjust for the thin cloud cover. In this way, several videos were recorded per filter, the majority of which had to be stopped well before the 30-seconds limit. The remaining movies, usually with no more than a few thousand frames, were subsequently stacked and the best chosen for further processing. In the end the RGB stacks were combined into a colour plate and the L-stack used as luminance. Finally in PSP the colours were corrected and the brightness increased. The whole image was constantly processed as a whole to maintain the difference in brightness between Saturn and Jupiter. Jupiter also shows the moons Ganymede (left) and Europe. Io was in front of Jupiter at the time of the image, its shadow is just visible. Nicolàs

If you exclude the construction costs of the dome and observatory itself, the DIY-automation would cost about: - Silent electro-motor: €250,- - Velleman-kit (not pre-assembled): €40,- - H-bridge (of reliable components): €400,- - Switches and other electronic parts: €100,- - Drive chain and sprocket: €100,- So for roughly €1000,- you should be able to do the automation yourself. Which parts I used can be found on my website. Most of it goes into the H-bridge. It can be built for a fraction of that, but with risk of overheating and thus fire (see this video). Of course the dome and observatory needs to be constructed, the cost of which much depends on its size, construction method and materials (and whether or not those are readily available). Nicolàs PS: I just noted your remark that "It's also worth mentioning that I am completely useless when it comes to DIY and don't know anyone that would be able to help with diy stuff so it would have to be something which is ready off the shelf so to speak. " In that case it is better to forget about this... 😉

I built my own observatory and that has a wooden dome, which was not overly complicated to construct (I found creating the spiral staircase for it a bigger challenge). A friend of mine delivered a steering column of a Citroen Berlingo that now is an integral part of the drive-train of the dome and together with another friend I made the electronics needed for the LesveDomeNet implementation. The dome now runs flawless under SGP (although the dome-drive-routine of SGP could do with some improvements). Thanks to its wooden construction and being about 7 metres above ground level, I have no issues whatsoever with dew. 🙂 Nicolàs

Hi Shimrod, perhaps plastic packing boxes for machine tools are an option? They are available in many sizes. Nicolàs

Hi Giles, I have an Esprit 150ED and the same 'issue' as you have. So far I did not experience that the long extension of the focuser was an issue for its stability. Still I feared that, as you wrote, that the extended focuser could be (or become) an issue, while for those rare occasions that I wanted to do visual observing I really needed an extension. So I made one myself on my lathe from aluminium tube which adds 45mm to the focuser, and had it spray painted white (together with my GTT60 that sits next to it) to fit the main OTA. You can see the before (all is black) and after (white section in between) situations in below images. Now I am focusing at around 15mm on the focuser scale. Nicolàs

This evening we had a clear period which allowed me to test the two lenses under the sky. To start with I took two images per lens, one with the diaphragm fully opened, and one with it almost closed. First the 35mm lens with fully open diaphragm (exposure time 1.5s): Ouch, that does not look too well, quite a bit of halo around all objects! Then with its diaphragm closed (30s exposure): That looks much better, halos are gone! According to Astronomy.net the image has the following properties: Size: 9.05 x 5.12 deg Radius: 5.198 deg Pixel scale: 16.8 arcsec/pixel http://nova.astrometry.net/user_images/4230332#annotated Then the 25mm fully opened (1.5s exposure): Not bad at all, appears to be a better lens. Then the 25mm with its diaphragm closed (40s exposure): Also not bad. From these simple tests I would rate the 25mm the better of the two. The Astrometry.net results: Size: 12.1 x 6.85 deg Radius: 6.950 deg Pixel scale: 22.5 arcsec/pixel http://nova.astrometry.net/user_images/4230428#annotated I also used the 35mm with my GTT60 to see if afocal imaging increased the pixel scale: Saturn is now shown at about 72px diameter over it rings, so indeed quite an improvement (some 300%). Please note that this image is taken through my GTT60, a 60mm singlet (plano convex) objective, stopped down to 30mm, and a singlet (plano concave) eyepiece and that both were made to mimic 17th century standards. Nicolàs

Just had a look at his avatar and directly recognised it, that chap and his friend are a bunch of amazing students doing some great stuff: https://www.docdroid.net/7tBJvsw/eduard-mol-youri-ariaans-pdf Nicolàs

No, I did not as I wanted to capture the view of the GTT60 as an early 17th century observer would have seen, so without additional glass between objective and eyepiece. Now what is not visible in that image is how small the FOV is, but that becomes clear from this daytime image of a nearby (3km) church tower: The grey halo is the inside of the tube, so basically that already can be chopped off using a longer focal-length lens in the afocal imaging. Of course I could use a Barlow, but I expect to get a different view (perhaps I would need to try that first 🤔). Nicolàs

Glad you like it! 🙂 Indeed the image was taken with the telescope being stopped down to 30mm. The thing I found disappointing about the image is the pixel scale. I was hoping to get a larger image of the planets (I imaged Jupiter as well), so this 23px disc was smaller than anticipated. If the 35mm objective works as above, that would give me a disc of about 100px, which would be much better. This is the contraption I made to do the afocal imaging: The bracket is fastened to a 2" to 1.25" adapter that slides into the focuser. The aluminium plate at the right has a central hole in which a 1/4" screw holds the camera. The spring-loaded screws in that plate press the camera gently against the eyepiece. Nicolàs

Hi Vladimir, I have tried that kind of set-up with my 60mm Galilean Type Telescope (GTT60). I did that with the ZWO ASI290MC in combination with the ZWO 2.8-12mm zoom-lens behind a plano-concave eyepiece: As you can see the result was a bit disappointing, although it is exactly capturing how the FOV of the GTT60 is experienced. Using the 25mm or 35mm lens I would expect magnifications like in the Bath-interferometer, but would need to test that once the skies clear again (if they ever...). Nicolàs

Here is a centre-shot in green, magnified 400%: With a 2.9 micron pixel-size this is not too bad, the light only covers maximum of 3 pixels. Nicolàs

Hi Vladimir, yes, can do that, but what do you want me to do exactly? Obviously these 20 euro lenses are not Takahashi-quality, so expect a lot of coma and other issues. This morning I already took a bunch of pictures of my 9 micron fibre-optic artificial star at 5 metres distance that I can send you. Those were taken in red and green (my artificial star can do RGB). At the end I took two images with the 35mm lens, one with the diaphragm fully open (left) and one with it nearly closed (right): The exposure times differed between them to compensate for the stop. I focused as well as I could on the blue label (the artificial star is in front of it, you may notice the green light from it). Obviously there is a lot of difference in sharpness and blur, especially noticeable around the fibre-optic cable. So questions for the test: - artificial star collimated or not?; - diaphragm open or closed?; - which colour(s); - through-the-centre shots only or also corner-shots?; - how to focus (corner shots same focus as centre shot, or re-focused)? Here is an enhanced image of one of the corner-shots in green and focused at the centre of the FOV (upper-right corner, magnified 400%): As you can see there is a D-shaped artefact around the light source. Nicolàs

Hoi Ed, welkom op dit forum, veel plezier hier! Nicolàs

Finally I ended up in China, where I found the following two lenses of respectively 25mm and 35mm focal length: - Fujian 35mm F1.7 CCTV TV Movie lens - Non-branded 25mm f/1.4 CCTV C 1/2 Lens I ordered them on 2 December and arrived yesterday, so 10 days later. Both came with four adapters to go from C to CS mount and two to go to Nikon mount. Despite their large focal lengths they are still quite small: At the left are the ZWO 2.1mm fish-eye and the ZWO 2.8 - 12mm zoom-lens, at the right are the 25mm (left) and 35mm Fujian lenses. The first impression is very good, they seem to be well made, run smoothly and fit the ZWO camera well. Most important is of course the image scale that I was looking for. Being slightly larger than the ZWO zoom-lens, I first had to modify the brackets for the Foucault-contraption. Once finished I took the following images: As can be seen there is quite some improvement, even more than expected. I anticipated that the 25mm lens would provide an interferogram twice the size of the 2.8 - 12mm zoom-lens, but in fact it became well over 3 times as much (327% to be more exact). The 35mm enlarged it even by 442% (1.35 when compared to the 25mm lens). As a result the 35mm lens produced an image too large to fit the ZWO ASI290MC chip (sensor height 1096px), so I am glad I ordered both and now use the 25mm for the tests. Next step is to see how they perform under the sky... 🙂 Nicolàs

Hi John, there are indeed a lot of parts that can mess up the collimation. They all need to be aligned, which is not too difficult as long as you keep the right order: - collimate primary mirror (without using a focuser and focuser tilt adapter, and preferably with them being completely removed) - adjust the focuser tilt-adapter - coarse collimate the secondary mirror - verify the inter-mirror distance - fine-collimate the secondary mirror If you then insert the HG-laser you should have nice concentric rings. On a new scope the inter-mirror-distance should be fine and could be skipped (although it never hurts to test it). Once or if correct, changing the inter-mirror distance can be avoided when only using two of the three adjustment screws of the primary and by not changing the orientation of the central bolt of the secondary mirror. So first mark the screw of the primary that you are not going to use (e.g. with a dot of paint), so that the next time you know which one not to touch again. Likewise mark the central screw of the secondary (with a dot of paint on the edge of the screw and on the edge of the hole, see below image), so that you can see next time that it still has and maintains the right orientation. Of course you will need to remove the secondary for the first step in the collimation process, so either count the number of turns that were required to remove the central bolt of the secondary mirror or (and I think that is preferred), measure the distance from the secondary mirror to the spider using a caliper on four locations like this: When only counting the turns of the central screw it is essential to mark the orientation of the secondary mirror as well (although it is good practise to measure it always as a verification). In above image two pieces of masking tape can be seen above the caliper with blue marks on them indicating its orientation. Nicolàs

Hi John, based on all the excellent info given in this thread I made a step-by-step plan, which I tested on a RC8 and published as an article on a Dutch forum (if you open it in Chrome it should translate reasonably well). Main importance is to realise that the tilt-adapter between the OTA and focuser should not be involved in the collimation procedure of the primary mirror. Instead the adjustment of the tilt-adapter should be done once the primary is in collimation. We even removed the tilt adapter during the collimation of the primary, but it can be done with it in place as long as the temporary peep-sight in the visual back is near the mirror and not at the end of the focuser. This part of the process is also explained in above mentioned article. You may need to make yourself a few tools as described in this thread and in my article, but once you have those, collimating the RC8 is easy. Nicolàs

Hi Stargazers, I am considering buying a ZWO ASI178MM for my Lunt LS80THA (80mm f/7). If I did the maths right it will just not allow me to do full-disc images, so I would need to get myself a focal reducer/flattener. Now I have at least two options: - Lunt 0.8X Reducer/Field Flattener - TeleVue TRF-2008 0.8x Reducer/Flattener I have very good experience with TeleVue Barlows (own the 2x and 4x PowerMates), but none whatsoever with its reducers or with those by Lunt. I would therefore love to hear your experiences with both of them. Thanks, Nicolàs

Hi Richard, I use a ZWO ASI174MM with my Lunt LS80THA and am considering getting myself a ZWO ASI178MM. First a few images: The detail-images are all taken with a TeleVue 4x PowerMate, even though this means I am significantly oversampling (optimum is f/17.5, using a 4x Barlow means I am imaging at f/28). The ZWO ASI174MM gives me the advantage that I can do full-disc with my LS80THA without a reducer, something that is not possible with the ZWO ASI178MM. Downside of the 174MM is the resolution, which is quite low (1936x1216) compared to the 178MM (3096x2080), that is the main reason why those full-disc images of @Nigella Bryantare so fabulous (or is it the processing skills?)! 🙂Downside of the 178MM is that there are reports of issues in H-Alpha where the camera causes a kind of grid pattern. For me that is the main reason why I am hesitating getting one. Also I would need a 0.8x reducer to go full-disc (and I have no idea whether to get one from Lunt or from TeleVue). HTH Nicolàs

Hi Vladimir, no, this method was not known to me (yet). I am going to dive into that. Funny thing is that the main purpose of this 300PDS is to use it as an artificial star, although I did create a Dobson mount for it in order to use it for outreach in the field. When used as an artificial star a 9 micron fibre optic cable sits centred in the focuser, which is focused at infinity and in that way it does a great job. 🙂 Nicolàs PS: just found your post regarding the Roddier test, very interesting stuff indeed:

A bit off-topic perhaps (so apologies for that), but during the past few weeks I have been building a bath-interferometer and a few days ago, after having first having tested a Bresser 130 f/5, I decided to place the before mentioned SkyWatcher 300PDS in front of the bath. I took 640 images to calculate the mirror's shape using DFTFringe. These 640 images were taken methodical: the mirror was rotated along its optical axis 8 times, so a set of images was taken for every 45 degrees of mirror-rotation. For each mirror-rotation I also rotated the interferogram 8 times, so the fringes were oriented in 8 steps of 45 degrees. The each fringe-orientation was imaged 10 times to get a good average and to be able to filter out some 50 bad igrams based on RMS (the median RMS of this set-up is about 0.1 lambda with an estimated standard-deviation of 0.02 lambda, so I rejected all igrams with an RMS larger than 0.15 lambda). The following image shows the 8 mirror-rotations in the top row and the same mirror-rotations below it, but then de-rotated: And this is the final plot (average of above 8 de-rotated ones) of its surface: The 300PDS has quite a bit of astigmatism and although I did not test the mirror of my C11 SCT, I think I this may well explain why the C11 performs better than my 300PDS Newton. Nicolàs

Hi Mick, My ZWO ASI1600MM Cool Pro, ZWO ASI174MM and ZWO ASI290MC also live in the observatory all year round (since 2018), the 1600 is permanently installed, while the other two just wander around, but hardly ever leave the observatory (occasionally they spent a few days holiday in the heated garage doing collimation and mirror testing stuff). All cams are disconnected when not in use. The observatory itself is not climate-controlled, during lousy weather conditions the scopes and ASI1600 live under a Geoptik cover together with a 65W Intel NUC pc to keep them warm (less cold is a better description). The other two usually sit somewhere on the dome's ring with a dust-cap on. So far all three live a happy live, no complaints so far and they still look and perform like new. Nicolàs

Hi Vladimir, great finds, thanks! I just contacted the seller. That lens should well double the image scale. cheers, Nicolàs

Dear stargazers, one of the cameras I use in my observatory is a ZWO ASI290MC, which I bought together with ZWO's New CS lens 2.8mm-12mm F1.4. Although this lens is not really suitable for astronomic imaging it gives me plenty pleasure for other purposes for which I want to use a small astronomical camera, like the odd meteor shower or other wide-field images that do not require the highest quality. Last week I started using this lens/camera combination for a bath-inteferometer and for foucault testing and found out that it does work reasonable well, but the image scale is on the low side: These two images are true to scale and show the 130mm f/5 tested mirror as a circle with a diameter of about 275px, while the ZWO ASI290MC has a resolution of 1936 x 1096 pixels: So now I am looking for a way to increase the image scale, so that the full mirror takes at least half the image height, but preferably 75%, and I was hoping that some of the forum members have experimented with other low-budget C or CS lenses or a barlow to increase magnification. Thanks! Nicolàs

In my Esprit 150ED those screws have nothing to do with how the 1:10 drive works and how it grips the 1:1 axis. If you check the images on my website, you will see that the 1:10 knob is mounted on a thin shaft, which sits between 3 bearing balls. These three balls are wedged between that thin shaft and the conic outside of the outer stainless steel bushing. Pressure is increased by rotating clockwise the brass ring-nut (which pulls the central 3-hole hub), but you will need a special tool for that (and first get rid of the lock-tite kind of sealing). Care should be taken not to apply too much pressure as that may create dents in the central shaft. Care should also be taken when dismantling as there are 18 tiny bearing balls below that ring-nut, which will wander off in 18 directions.... 😉 So make sure you work over a tray to catch them balls. I have serviced mine and now it easily holds a diagonal and a TeleVue Ethos 21mm or PanOptic 41mm, both weighing about 1.2kg. Nicolàs