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cwis

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  1. Yes! I appear to be part of the collective - mirror diagonal arrives today hopefully! Thanks again for the help and advice!
  2. After a frankly disappointing session with my ST80 a couple of days ago I put the question to the SGL hivemind: I received a LOT of helpful advice (lose the contrast booster filter!) and some suggested targets to try and gain some appreciation for the poor maligned thing. As last night was promising to be mostly clear I scribbled a target list down from the suggestions and grabbed the 'scope and went outside about 2130. I synced the AZGti with SkySafari for ease of use and began straight away - no cooldown time at all (a novelty!) I only took one eyepiece with me initially - my 24mm UFF. Stock 2: Straight away I could see the difference that removing the filter had made. St2 was a scatter of tiny pinpricks of stars, interspersed by larger brighter ones. Also in the same view was Struve 26 (Skysafari identified it as HD14172 and a bit of web cross referencing showed the Struve catalog ref) a lovely and obvious widely split double. I observed the vista for quite some time getting my head around the tiny, tiny sharp stars being shown by the ST80. Many more than in any binocular view (and my arms weren't shaking) and all so sharp... More stars popped out as my eyes acclimatised and the impression of depth grew. Kemble's Cascade: This was just a name to me when I typed it into the seach bar on SkySafari (I didn't look up any of the targets in advance) and my notes read "Near vertical line of bright stars leading to NGC1502 (thanks SkySafari for the id.), with a dusting of dimmer stars visible to the LHS of the asterism. Wish I had darker skies". NGC1502: Tiny pretty open cluster. Two closely located bright stars visible instantly with a scattering of dimmer stars getting more numerous the longer you look. Wiki says there are 45 - I'll have to have a count next time! This next one wasn't on the list of advised targets but should have been - it did it for me. Wow! Double Cluster: This looked at first glance like a very large single circular open cluster bisected diagonally by a dark line of lower star density. As I looked longer the two clusters kind of resolved themselves as separate - difficult to explain! A truly amazing sight with hundreds of tiny pinprick stars visible and the two clusters together nearly filling the view at 17x magnification. I decided to revisit Andromeda without the contrast booster and could easily see M32 - still haven't located M110 even with goto assistance. NGC752: Gatekeeper stars 56 And and HR556 show the way to this delicate roughly circular open cluster. Again a feeling of depth started to occur as more stars were resolved as I observed longer... M103: I revisited this target again now I'd removed the contrast booster. Navi was visible in the same view and the cluster was very small, but different star colours were visible... Excellent! At this point I thought I'd test the kit a bit and pointed at Capella - a nice bright star. At 17x magnification I could see a horizontal diffraction spike I'd not noticed before. I tried to compare the view without the diagonal but I don't have sufficient focus travel. At 50x magnification (42-8mm zoom) I could see vertical and horizontal diffraction spikes along with a smattering of CA and what I think was atmospheric refraction (blue on one side and red the other)- or maybe colour wedge? Maybe I need to settle the objectives as suggested. Capella was 32 degrees above the horizon at the time. I thought I'd try and split Polaris and this time found the secondary - I think it was hiding before in a diffraction spike. Tilting the diagonal brought it out but it was very faint. NGC188: I've completely failed to find this a number of times star hopping with the dob. While I was here in the region of the sky with Goto I thought I'd have a look. I matched up the marker stars against SkySafari and I could see a very few of the brighter stars in the cluster. I'll have to return with the dob now the position is clearer... Uranus: While I was waiting for the Pleiades to clear the trees I did a goto to Uranus - just to tick it off my list really - I observed Neptune a few weeks ago. I wasn't expecting much, and didn't get much! Just a star in the right place in the view in relation to the background stars... Pleiades: Now this is more like what I expected from the ST80! Filling the field of view, large bold obviously related stars. Looking white rather than blue but totally captivating. I didn't detect any nebulosity but I don't think I can expect any at this aperture. I'm not sure the neb I've seen with the dob is anything more than the powerful beam of light from the eyepiece lighting up the murk in my eyeball! I took a last look at the double cluster before packing up at midnight. Wow! I think I need to get a mirror diagonal...
  3. Hello! No - I see no need really? With a cheshire it all looks lined up now (Had to file a few screw holes and remove some paint though!) and I get lovely concentric diffraction patterns on stars? What fault would I see with misaligned objectives?
  4. Hi Andrew - the diagonal is the 90 degree one. I was out again last night and noticed the prism was giving me me noticeable diffraction spikes on brighter stars, so perhaps I do need to look at a decent mirror diagonal. I found the reason I couldn't see Polaris B during the previous session was because it was hidden behind a diffraction spike!
  5. Wow! Didn't expect so many responses - thank you all for your input! Maybe I am being a little unfair comparing the st80's light pint glass to my dob's lightbucket but I thought that (apart from Polaris) I had chosen some targets that would allow it to shine. My impression was that whereas wide open views showed lovely bright stars, once enough mag was added to frame a subject (M103 in particular) the view had dimmed too much for me. I do like how stars "pop" into focus though! The erecting prism gets pretty good reviews on FLO and I quite liked the idea of right way up stars - I also used it on my holidays for terrestrial observing where the ST80 was really great actually. I can't see any of the artifacts associated with prisms with my particular example. I'll remove the contrast booster in case it's dimming the view too much (hadn't thought of that, and it's yellow so maybe it's removing colour from blue stars? Dur!) and have another session. Feel free to add to the targets below: M45, Stock2, Hyades, Kemble’s Cascade and Melotte 111 (never heard of this one!) and the next clear night I'll go out again with just the ST80. If I manage to "get" widefield views then I'll get a star diagonal. Oh - and @MalcolmM - try a dob! Wherever I point mine I see stars. Hundreds of stars!
  6. Hi all, I picked up one of these a while ago and keep setting it up on my AZGTI and then wandering off and observing through my 10" dob. I think I pointed it at Jupiter once when I first got it a few months ago and compared the views directly with the Bresser and saw a ball of mush instead of the GRS and barges and suchlike, but this was entirely my expectation and it was for star fields etc... Completely the wrong target. So last night I decided to only take it out and look at more "ST80" type targets. I was completely underwhelmed! Andromeda: Dim binocular type view. Couldn't make out M32 or M110. M32 is clearly visible with the dob.... Polaris: Tried to make out the dimmer companion star that's obvious at 50X mag with the dob - nothing whatever I did. I'm seeing nice concentric out of focus diffraction patterns so it's collimated (which I had to do when it arrived as it was banana shaped) but is contrast lacking? M103: Only a few of the brighter stars visible. Was small with 24mm eyepiece and got dimmer with any magnification so no colours were perceptible. This is amazing with the dob - bright red and blue stars filling the field of view and more dimmer stars the longer you look... Pleiades: OK - it fitted completely in the view which is something the dob cannot do. But the view is so much dimmer and all the stars are white, not blue because of this. In fact this dimness was a constant theme of the session - I was continually turning my red light away or turning it off as it felt like it really intruded - not something I've ever experienced using the dob. So, Is it me? The AZGTI came with a 130mm F5 newt that I personally think is better in almost every way (now I can collimate it) - it'll have a honest go at a planet (saw Mar's polar ice cap with it) it'll show all of the Pleiades but nice and bright and blue, I've split doubles with it (Polaris is easy at 50x!) etc etc. It has coma but the ST80 does not have a flat focal plane so they on a par with stars in the corners of the view, really... Also, it's far more comfortable to use - the tube is fairly short so the height of the eyepiece although obviously variable is easily accommodated by my drummer's throne (as is the dob). However the height variation required to use the ST80 appears to be far larger, even after turning the diagonal sideways. So what am I missing with the ST80? I was using a Baader contrast Booster and a Williams Optics erecting diagonal... Am I just a (don't giggle) confirmed dobber? Is it my rubbish eyeballs? Is my sky not dark enough (Bortle 5)? Anyone want a lightly used one?
  7. Three whole weeks since the last proper session due to holidays, offspring and clouds! Managed to get out sometime a few weeks ago to test this: It's a 130mm F7 newt built with an SvBony metal focuser, some mirrors from Astroboot, a plastic duct pipe and some 3D printed adapters hot glued in. I've already got a 130mm F5 newt but I wanted to be able to understand the difference that a smaller primary obstruction and a longer focal length makes to viewing, particularly with regard to planets. I printed the above very dodgy tube rings and dovetail to take advantage of the last clear day we had a few weeks ago and mounted it on my AZGTI where it swayed, precariously: I managed about 15 minutes with it on Jupiter to check it was all OK after collimation and could easily see bands etc and plenty of contrast, approaching what I get with the 10 inch dob even with the mount wobbling about so very promising! I'll build it into a dob mount I think as it's pretty heavy and this is supposed to be a budget project... I also tried my ST80 on a terrestrial target while on hols and was amazed by how little magnification you can get away with: In the distance out to sea behind the small human experiencing the beach for the first time is a ship called the Sea Puma: It was 8.4 Nautical miles away and I could clearly read the name on the bows with 50x magnification, but contrast was very low because of the 15.5Km of soup I was looking through. - it was looking through fog! And on to last night! Got the 10inch dob out about 2200 and let it cool for 30 mins - temperature was around 10 degrees C and it was quite windy - wore the winter coat! Started with Polaris to check seeing and collimation - 'scope was fine, sky looked transparent but quite turbulent. I decided to take advantage of the time before the moon rose above the trees to look at Andromeda as it's the first time it's cleared the trees since I've had the dob! The core of Andromeda was VERY bright (24mm UFF so 50x) and M32 was also clearly visible (see bad sketch!) but I couldn't find M110. I wasn't sure whether I could see some Andromeda structure or whether it was the moon lighting up the sky around the core (more likely looking at photos after the fact - M32 is very central) . Next on to the Circumpolar sky :- I tried to spot NGC188 as recommended by Turn Left at Orion but I think the sky was too bright as the moon was looming. I decided to spot some doubles: Pi1 UMi (HR5829): Mental note - when planning these jaunts always look up the targets before the session to get them in a format that SkySafari and I understand so I have a chance of finding them... I still find comparing the diagrams in the book in the dark to the view in the finder very hard so the steer from SS is hugely helpful. I have to state that this is me, not the diagrams - once I'm oriented and have found the target they suddenly make sense! Wide clear vertical white/yellow double - obvious even at 50x Struve 1694: Book says white/white but I see more Blue/while horizontal double. Easily found star hopping. I wonder if my red light is messing up my colour perception - it is too bright? Herschel 2682: Favourite "double" of the night - a lovely symmetrical slightly squashed triangle - one white, one dimmer blue, one dim blue (looked red to me at first - WHY?) Apparently they are not gravitationally bound... On to Cassiopeia - I love this region of the sky - so rich in sights! M103: Initially sparse but very rewarding roughly triangular open cluster near Ruchbah - very nice at 50x magnification. I'm not normally a particular fan of open clusters but this is very pretty - The brighter half dozen odd stars are of visibly different colours and more dimmer ones pop out the longer you look. Stock 2 Open Cluster: This is a HUGE open cluster in Cas. I was packing the wrong telescope really - I could have done with the ST80 or even just binoculars. The views were almost better in the finder! I need to compile a list of targets for the ST80 for one night... Pleiades: First view of the season as it cleared the trees. Another ST80 target really. Last year I was sure I could spot nebulosity in between the stars - not this time but that may have been due to the moon... Packed up at 0030 as cloud started coming in.... Closing notes: Swapping between the 24mm UFF and the Seben 24-8mm zoom really shows up the off axis sharpness of the UFF. I really need to replace the Seben (was great terrestrially though!) but with what? A zoom or fixed focal length eyepieces?
  8. That's really not bad! I'm looking at building mounts for mine with bearings to minimise the errors and then calibrate them them in situ to get the accuracy I need. I'm up for saving a load of pain - do you have a link? Are they optical or magnetic? Absolute or relative? I keep looking at the Nexus you recommended - very tempting and I'd have something that worked straight away.... But I'll keep battling on for a bit - I'm having "fun".
  9. Quick update - I created a linearization jig to see how much the sensors drift using a cheap (very cheap!) NEMA 17 stepper motor I had floating about. It's 200 steps per revolution as you can see here. What amazed me was how uneven the steps were! They seemed to alternate between 1.7 and 1.9 degrees - they should obviously be 1.8. You can however see the signal on top of that noise - the sensor drift. It's cyclical, as expected and maxes out at around 0.5 degrees. I think I have one of those mini geared steppers somewhere - I may replicate this experiment with one just to remove a load of dodgy stepper noise and add (hopefully!) a much smaller amount of gear backlash noise...
  10. Hi @Pixies! Yeah I wanted somewhere to put my wittering without cluttering up the discussion boards. It makes me take observation notes and sketch a bit, which I've never done before, plus I tend to go outside now with a vague plan... A filter is next after a replacement for my budget 8-24mm zoom. I use it about 80% of the time so I either need to get a better zoom (it's not very sharp apart from exactly on axis which is frustrating in a dob) or start buying fixed focal length eyepieces - I only have a 4mm and a 24mm....
  11. Day 3 of minimal sleep due to child with cough. Hey ho... Set up and cooled for 2215 and had a quick peek at Jupiter and Saturn. Very mushy at the 6mm (200 odd) setting that did so well the night before. Decided to come back later and see if it had improved. Hopped from Enif to M2 and this confirmed that the seeing was far worse than last night - couldn't really resolve any stars. Let's do a couple of doubles! Struve 2848 in Pegasus: Wide separation, split at 53x. Yellow/blue starts of similar brightness. Tried to hop to Struve 2786 but overhanging branches were obscuring too many key navigation points, plus sky glow from London was obscuring key constellations to the naked eye. Frustrating! Moved to Altair (I could see this one as not over London!) to use as a starting point. It was a ball of angry fuzz at higher mags - no airy disk. H N 84: Orange/yellow primary with dimmer and very blue companion. very pretty! Wide split. Decided to stay in this area of sky therefore observed the Coathanger nebula - it was obvious in the finder but underwhelming at 53x - it didn't fit in the view. Like the Pleiades, another open cluster best suited to the ST80. I need to make a list of those and have a session with it at some point. Got lost on the way to Anser (Alpha Vulpeculae) and then spotted Albireo in the finder so stopped there for a while... M56: Small glob. Could just resolve some stars on the edges. The sky seemed quite bright or milky and the glob quite dim so upping the magnification didn't seem to increase the contrast as much as usual - the glob and the sky both dimmed! Dumbbell Nebula: Finally found it - was looking last night. Much bigger than expected but quite faint against the milky sky. Swapped out zoom for the UFF to see if I got more contrast. Not really but it did look perceptibly blue at lower magnifications. Maybe my imagination, don't know. It looked more "coke can" than "dumbbell" - like a rectangle in a faint circle as per poor sketch: M71: "Coarse" globular cluster. Quite big with readily resolvable stars. Took magnification well - far better than M56. Last look at Jupiter - still really fuzzy so packed up at 12:07.
  12. Started around 2200 - proper dark at last. It was warm - shorts and t-shirt. No wind - total calm. The seeing was weird - wobbles due to the heat, but clear and transparent. Stars were points, not fuzz, but wobbled about. Larger convection cells or something? Saturn: 4mm (317x) Nirvana misted up in seconds - not impressed! May have been caught by dew - grass was wet. Put it in my pocket to warm up. Backed off the mag and tried the zoom at 8mm (159x) but the seeing wasn't great. A band visible on the planet (looked like a cummerbund position wise!), the Cassini division (Cd) was fleeting visible, more on the RHS of the planet for some reason? Tried 24mm UFF with the barlow (106x) and got a very sharp image - wobbly but sharp. I like the view through this combination - very crisp wide sweet spot for minimal dob nudging. Cd was visible but the whole planet was shimmering in the heat haze. Experimentation showed the best views were with 12mm zoom setting with barlow so 6mm (212x) - a crisp but wobbly planet with the Cd very clear on occasion, and a band of darker tan/brown just below equator. 3 visible moons. Jupiter: Kept 6mm setting and moved to Jupiter. GRS clearly visible, bands all nice and clear - seeing very good. Jupiter was just clearing fence/lattice so expecting improvement when diffraction effects subside... Noticed "double star" effect of Ganymede and Europa being very close together in view. Tried the contrast booster filter at this point - made no difference really and colour cast annoyed more than last time so removed. Decided to search out some doubles and practice star hopping while I waited for Jupiter to rise to a more useful position. M2 Glob in Aquarius: Hopped from Enif which was just visible in the Rigel. 24mm (53x) Just a blob. 12mm - some granularity around the outside, 6mm, diffuse core surrounded by resolved stars. Seemed to move quickly at this mag - conscious of constant nudging. M2 is enjoyable to observe - a real impression of 3d depth and the longer you look, the more you see! 2316 - bye bye Saturn - vanished over neighbours roof. 2320 Jupiter: Seeing now good! Observing what I think are two barges on surface - one nearer the middle red/brown the other closer to the edge brown/red (dob view). Are these barges? Never had such a clear view of Jupiter so all these features are new! 4mm now warmed in pocket was OK but views best at 200x odd with barlowed zoom set to 12mm. More star hopping - aiming for Dumbbell Nebula but got lost. Reoriented on Delta Sagittae after some moderate faffing. Nice wobbly but clear Airy yellow disk - seeing therefore pretty good! Gave up on Dumbbell, thought I'd visit some old faves so pointed at Vega and on to the.. Double Double: Clearly split both pairs at 8mm (159x). Just split (an honest no really, I can see a black line split) at 18mm (70x). Sheliak (Beta Lyrae): White with very blue quite dim compainion. Striking contrast! Ring Nebula. I'm sure that the centre looks blue at lower magnifications. Is that possible from a Bortle 5 sky or is my brain filling in or the red observation light affecting my colour perception? it looked more "filled in circle" and less "ring". Packed in at 0010 - small child ill so need rest. Check out the light pollution from London.. 0400: Awake comforting child - she has now dropped off. Nice! Saw Orion through window so snuck out with binos for a quick peek - first of the year. All seems to be present and correct - Betelgeuse seems brighter again? Rigel still a double. M42 et al still there. Good!
  13. I've got the 4mm - I find eye position fairly tricky but once there the views are nice and sharp and wide - great for a dob. A daft question for other Nirvana owners though: My 4mm mists up at the drop of a hat! I just have to look at it and boom I'm looking at Jupiter through a halo. Keeping it in my pocket until I want to use it helps, but it's the only eyepiece I have that I have to do this with - even last night with temps in the high teens.... Anyone else noticed this? I keep looking at the rest of the range but this is putting me off...
  14. First field test! Zip tied all the components to the alt encoder mount and tried it out last night. The current code zeros the encoder positions on boot so setup is basically point the scope North and level. I used Polaris to get North. One idea is to zero the encoders and then offset the elevation to Polaris so I could point to that on boot, but that ties the setup to my current latitude so maybe not... I've put all the gubbins on the opposite side to where you sit to keep it all clean but this may have been a mistake... Power it up and connect using SkySafari. I did my first alignment on Polaris and Caph and then tested with a few PushTos and some "sky browsing". I need to read the SkySafari instructions again re: alignment but I got there in the end. PushTo tests: I thought I had issues with both axis but this was quickly diagnosed as being caused by a wobbly paving slab (dur). Alt looks fine but I have a periodic error in Az that makes it about 2.5 degrees out over 180ish degrees of travel. (Polaris to Vega for example). I think it's related to poor centering of the Az encoder over the az magnet, as moving back 180 degrees to (Vega back to Polaris for example) completely removes the error. Vega was still in the finder but that's not good enough for DSO. Keeping the pushto to within 90 odd degrees Az of Polaris allows a sub degree pushto accuracy - Polaris to M81 put M81 nearly in the middle of the 8mm 160x (0.38 degrees) view. Maybe 0.1 degree accuracy? If I could get that across all the sky I would be very happy! With Alt I'm within the encoder manufacturers 0.5mm positioning error and I'm using their supplied magnet. Due to the size of the Az bolt etc I don't think I've postioned the encoder with the same degree of accuracy and I'm using a different magnet. I'm also getting more noise on this axis than I should so something is not right. It should be pretty easy to run some tests during the day so I'll start there. Edited to add: One option would be to add some linearization code - I'll work out a test rig. Some other ToDo: Mask the Microcontroller. It's really too bright! I was going to use white ABS for the enclosure but maybe black would be more appropriate. I'm wondering whether I'm using a pin that has the on-board LED attached to it - if I turned that off at least then it would glow red and not blue! Thinking of putting all the electrics in the bottom of the encoder mount so they are masked by the dob mount when in use. Setup/Teardown Streamlining and Stowing. I need to make the boss of the spider deeper so you can undo the centre bolt more to get the alt encoder off the bolt without detaching the spider completely. It would make setup and teardown easier as the assembly would stay attached to the dob base. Along the same vein I need to round or shorten the base of the assembly to allow it to pivot round the spider bolt to a stowed position. Looking at the weather I should be in a position to test the updates when another clear night appears! Phone/tablet Mount: Was continually picking up and puttng down the phone. Would it be a good idea to move the encoder mount to the viewing side of the dob and putting a handy shelf on top for the device of choice so you can just glance down? Food for thought.
  15. First session for 12 days. A short one because I could see clouds slowly approaching and the moon would be up shortly (but not visible from my garden). Set the telescope up far earlier than last time and allowed it to cool with the covers on. As it was still nice and light I attached the latest version of the encoder mount and zip tied the processor and power supply to it. I set up at the south south west end of the garden with the intention of looking at some doubles near and in Cassiopeia and giving the encoders their first real test and trying out my new book: The book finder views are aligned to astronomical North which for some reason I am having difficulty getting my head around. How else would they be oriented? Why am I finding it disorienting? Eta Cas: Easily found just using the Rigel. White primary - Orange (to me) secondary at 5 o'clock (dob view). Wide separation - obvious at 24mm (53X). Seeing not great - more magnification didn't really make things any clearer. Had a quick look at Jupiter (just visible) and that was a blurry mess - should I have given the scope more time to cool or was it seeing? Sigma Cas: First PushTo. Need to read the instructions again but couldn't align to Eta Cas after picking up a pointing error. But just moved scope to the same offset away from Sigma Cas and it was the brightest star in the 53x view. Cool but not ideal... Tighter double - no split at 53x. In fact it was difficult to see it was a double at that mag with positioning errors over the eyepiece and coma if away from the centre of view masking the bulge in the primary. Split was clear by 18mm (70x). Stars similar white blue colour - primary maybe bluer? Messed around with pushto and encoders for a while at this point testing. Feels like I'm wasting good observing time but I need to do it if I want to complete them. Polaris: (In focus for once!) Seeing seemed to have improved as was spotting signs of airy disk in the primary at higher mags and the secondary a lovely sharp pinprick of light. Obvious even at 50x. Collimation looked loads better than last time (maybe more contrast?) but totally forgot to test in situ with the Cheshire. Moon was up now and washing out the sky but was not visible from my location. I could also see clouds approaching... M81: Aligned again on Polaris and Caph and tried a pushto to M81. Was in view at 8mm (160x) Wow! Hope that's repeatable... No real shape was visible (unlike in the past with this scope) due to the moon and probably Jupiter washing it out. It looked like a mini Andromeda. The sky was basically blue at this point! Kochab: Final Pushto to Kochab. Lovely Yellow bright star - no visible Airy disk but nice symmetrical twinkle. Notes: Dob action feels sticky. Not really noticed before but now I'm trying to do sub degree pushto moves it's more of a pain. Both Axis - seek advice! Need to mask light from micro controller and power source. Need to work out how to take decent notes - have a method and stick to it. Book is excellent - need to work out finder views if I'm going to use it as a star hopping guide which looks like it would be part of the fun. Would be a bit of a waste just to use it as a list of interesting targets and use PushTo. I'm really loath to mark it with pencil too - it's too pretty! Moon and Clouds push me indoors:
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