lenscap

For a thin walled cylinder such as a telescope tube the bending deflection is inversely proportional to (Young's Modulus x tube wall thickness). But Young's Modulus for steel is typically about 3 times that of Aluminium. So for tubes of the same diameter, an Ally tube needs to be about 3 times as thick as a steel one for the same rigidity, which manufacturers are well aware of.

Hi Jason & welcome to SGL. I assume you are mostly interested in visual observing. The Skywatcher Skyliner 150p Dobsonian would give you the maximum aperture for your money & is only slightly over your budget. skywatcher-skyliner-150p-dobsonian It can be fitted with a Skywatcher motor focuser.

I didn't know Tiger Tanks had stereo sound systems. Or do you plan to blast out 100watts of "The Ride of the Valkyries" to scare the hell out of the enemy model tanks? 😀

I noticed that ENS have one; http://ensoptical.co.uk/lx90-handset?search=autostar No connection. . . .

Free bits from unfinished 1960's Newt self -build for collection from Dorset available on AB&S. Seems to include figured, but presumably uncoated 8" primary. https://www.astrobuysell.com/uk/propview.php?view=154340 No connection.

Skysafari lists Delta2 Lyrae as a double, with magnitudes 4.28 & 11.20, But search stelledoppie.it and this is a summary of the result; a multiple with 11 components potentially visible in an amateur scope. This is my plot of the above data. With a 200p F/5 in Bortle 8 skies/ average seeing, I have seen the 6 brightest components to mag 10.30. The mag 11.20 should be doable but has eluded me so far. I think that for my setup, the dimmest 4 stars will need darker skies or better eyes 😀 If you are observing Delta2 Lyrae, how many components can you identify?

If you use 400 step motors and a 2.5:1 belt drive ratio, 32 microsteps would give a (theoretical) precision of 0.3 arcsec on RA, which is about the same as the factory Synscan Goto's achieve. 3 or 4 deg/sec is a good slewing speed. 10 deg/sec would be more like a missile launcher than a scope mount, but if the motors have enough torque, why not. 😀

I used type T2.5 Timing Belts & Pulleys from; https://www.beltingonline.com/timing-pulleys-bars-272/t2-5-pulleys-279/?zenid=8fkphh3cp60497d3o16aq3vkv3 On the motors; 15 tooth pulleys, bored to 5mm (check your motor shaft dia), each with 2 off M3 grubscrew holes. On the worms; 30 tooth pulleys, standard 6mm bore, each with 2 off M3 grubscrew holes. This obviously gives a ratio of 2:1 which works fine. If I was starting again I would use 40 & 16 teeth for a ratio of 2.5:1 giving more precision for a few pennies extra. I used these motor mounting brackets; https://www.ebay.co.uk/itm/3D-Printer-Parts-42mm-L-Bracket-Mount-for-Nema17-Stepper-Motor-Alloy-Steel One of these brackets mounts the Dec motor as is. I had to make a second angle bracket to fit the RA Motor+bracket to the mount. I suggest you mount the motors before ordering the pulleys & belts so that you can check pulley clearances & accurately measure the distances between the relevant shafts & calculate the required belt lengths. There is no room for error with these tiny belts. Here is a belt-length calculator; https://bepltd.com/pages/how-to-calculate-belt-length These are the belts I used, 6mm wide; https://www.beltingonline.com/t2-5-synchroflex-timing-belts-2903?zenid=8fkphh3cp60497d3o16aq3vkv3 Hope this helps. Out of interest, how many steps/rev are your motors and what microstepping options does your EQDrive controller allow?

Hi, and welcome back. A rough polar alignment is sufficient for visual observing & short-exposure snapshots. No need to see Polaris. Level the tripod, set the latitude bolts for your location. Point the N leg of the tripod North as best you can, for example, using a compass (google the local magnetic variation), app or local map. Select Siderial speed for stars or planets & this will keep the target in a low or medium-power eyepiece for hours. Here is a smart-phone holder. https://www.firstlightoptics.com/adapters/celestron-nexyz-3-axis-universal-smartphone-adapter.html Here is the manual for that scope; https://s3.amazonaws.com/celestron-site-support-files/support_files/AstroMaster-EQ_Telescope_Series_Manual_Web.pdf Good luck.

Many of the stars listed as doubles in Skysafari, Stellarium & the like, are actually multiples. You can identify which have further components which may be within the reach of your scope using stelledoppie ( 200p F/5, EQ3-2, diy Onstep Goto, generic Plossls. 19th Sept, from 22.30 BST, Transparency - good, Seeing - average, rising 70% Moon) I observed several multiples in Lyra. HD 172131 This is a Quadruple (Mags 8.06, 10.63, 10.45, 12.81 Spacings 16",210",38") The first 3 were visible in a 10mm EP, the 4th eluded me. HD 178592 A Triple (Mags 8.57, 9.02, 10.84 Spacings 2.3", 99") The tight pair were split at x200 with the dimmer third just visible to the SE. HD 174638, Sheliak has no less than 8 components of which 6 are potentially visible in an amateur scope. I could see 4 ranging from Mags 3.63 to 10.62 with the dimmer 3 arranged in a near equilateral triangle and the bright primary close to bisecting one of the sides, giving the impression of a triangular pyramid. No surprise that the 13 & 14 Mag components were not seen . HD 175588, Delta2 Lyr Has 11 components which are part of the Stephenson 1 asterism, laid out in a ragged zigzag line over about 6 arc min. I could make out 6 of them up to Mag 10.3 at x100, and maybe the 11th Mag 7th by AV but it could be my imagination. STF 2474 which with STF 2470 makes up the well known Double Doubles Double is itself a triple. (Mags 6.78, 7.88, 11.42, Spas, 17", 264") The dim third was visible by AV. HD 179709 is a Quad (Mags 8, 9.1, 9.7, 11.47 Spaced at 10, 71, 74") with the 11.47 star visible by AV, the dimmest I have seen with this setup. STF 2430. Just a plain old double to finish. (Mags 8.94, 9.18 at 1.5") easily split at x200 and the closest pair I have yet split with this scope, helped , no doubt by the lack of glare due to the dim but near equal magnitudes. After a really enjoyable couple of hours on a lovely, mild night I now have a much better idea of the capabilities of this scope at my location. And with the possibility of moonless nights, better seeing & perhaps better dark adaptation there is plenty of room for improvement. Onward and upward! 😀

I assume that you have either the "Dual Axis Motors" or these "Enhanced Dual Axis Motors" sold under Skywatcher or several other brands; https://www.firstlightoptics.com/sky-watcher-mount-accessories/enhanced-dual-axis-dc-motor-drive-for-eq3-2.html These are OK for converting a manual EQ3-2 into a tracking mount but I would NOT recommend them as the basis of a GoTo system. It can be done and It has been done, but these motors are not capable of being driven fast enough to produce a satisfactory GoTo system. It would be very sluggish at best & I believe you would be disappointed with the result. I believe that EQDrive sell motor kits to go with their controller. I haven't used them myself but assume they would be fit for purpose, although maybe expensive. I built a diy GoTo system for my EQ3-2 based on the open source OnStep project using a pair of NEMA 17 stepper motors and belt drives. Since you already have the EQDrive controller you would not need the OnStep software or controller, but there is enough information in the Wiki to enable you to select motors & drives for yourself if you wish, which would be a lower cost solution. onstep@groups.io | Wiki There is another similar project, AstroEQ, which may be of interest. Tutorials & FAQ’s Food for thought?

"It's Earth Jim, but not as we know it." 😀

Hi, and welcome to SGL. The EQ3-2 RA worm gear ratio is 130:1 and the DEC is 65:1. The other parameters will depend on which stepper motors you are using & what gear sets or pulleys & belts you intend to use to connect them to the worm shafts.

No I haven't. But basic reading glasses can be bought very cheaply. What if you removed the "observing eye" lens from a pair and wore them at the eyepiece. Would this work? It would avoid having to scrunch up your non-observing eye to grip the monocle. Whichever approach you try, SGL rules require that you post a photo! 😀

Hi Kronos, have a read through the thread below which suggests that this is the correct lens arrangement;

Look on the bright side. Weather forecasts are usually wrong! 😀

Hi mikeysweet, Have a look at this thread. Towards the end there are some suggested solutions;

My budget doesn't run to a decent frac. I made an 80mm off-axis aperture mask for the Newt. It removes the diffraction spikes and gives a more refractor-like view which is better on tight, bright doubles like Izar.

Decided to use the clear night to look at some doubles in Draco. 200p F/5, EQ3-2, Onstep Goto. Average seeing. Nu Dra, Kuma is the faintest of 4 stars of the dragon's head. With identical 4.85 mag components it is a binocular (62"), double known as the Dragon's Eyes (copyright Sissy Haas). Mu Dra, Arrakis is a 5th mag 2.6" yellow/white pair about 7* to the W. A tiny dumbbell at X100, it split cleanly at X200. 16/17 Dra is a wide 90" 5th/6th mag double a further 7* to the W. On closer inspection 17 just splits to reveal a third 3" component with a 10mm Plossl (X100). 31 Dra, Dziban, located on the Dragon's neck, has mag 5.7 & 4.6 yellow components seen in a 32mm Plossl with a faint unrelated 3rd nearby forming an acute triangle. NGC 6543, The Cat's Eye Nebula is a must when visiting Draco. I could only see stars in the 32mm but with a 10mm eyepiece one of the "stars" turned into a grey or bluish/grey slightly squashed disk about the apparent size of Saturn. Some planetaries don't look like planets, but the Cat's Eye does! It is easy to imagine you are looking at a giant planet rather than a tenous bubble of gas. With a star also visible in the 10mm FOV, this is an ideal target to demonstrate Averted Vision. Look at the field star and the Nebula brightens considerably, look directly and it dims. You can flick it on and off at will. 40/41 Dra, located about halfway between the Cat's Eye and Polaris, is a different type of cat's eyes, a 19" pair of identical mag 6 yellow stars looking like a distant feline at X30. 47 Dra is a fainter but wider, 8th mag, 37" binocular pair of eyes. 39 Dra is a yellow primary with a tight 3.7", faint 8th mag companion that showed a hairline split at X100. Epsilon Dra is challenging with a mag 3.8 primary & a 6.9 mag secondary seperated by 3.2". In average seeing with a wobbly primary star, I got an intermittent split at X200. Struve 2549 is a fascinating multiple with three main, subtly coloured, 8/9 th mag components each seperated by about 28" forming an arc with a fainter 4th about 55" away, all visible in a 32mm eyepiece. The colours are hard to pin down. I saw them as yellow/blue/white from E to W. Your mileage may vary. If you fancy a challenge and have dark skies & sharp optics the Eastern star is apparently itself a close, 2", double with a 12th mag companion! This was a really enjoyable 2 hours on a warm night. I am getting used to shirt-sleeve astronomy. The cold weather will be a terrible shock when it arrives. 😀

Hi, and welcome to SGL. You have an impressive Resume. I'm sure the forum will benefit from your experience.

Beautiful image, and it split Alcor/Mizar very nicely.

Hi PlanetGazer, You can import observing lists into the free version of Skysafari. If you import it from the online repository within Skysafari using: Observing/ObservingLists/Import from Online Repository it should just work. If importing to your PC or phone from elsewhere, make sure the list has a ".skylist" extension and place it in- <top level of SD card>/SkySafari/Observing Lists/ or, if using internal storage, Internal storage/Skysafari/Observing Lists/ This is for Android, iOS will differ. The Skysafari manual is here; https://skysafariastronomy.com/support/manual/manual.shtml Good luck.

The Sky at Night has been running more or less monthly since 1957! I think there has been extra "Space" stuff this year because of the moon landing anniversary. I've also been enjoying episodes of Nova on PBS, & lots of NASA based programming on Smithsonian channel.

8.50 Tim Peake , How to be an Astronaut. 9.00 The Sky at Night Guides - Galaxies. 10.00 The Sky at Night. Projects competing for a 2028 ESA launch slot. It's cloudy here so I'll be watching.

Following a mention on another thread I searched Previsat https://sourceforge.net/projects/previsat/ for any objects transitting the eclipsed Moon on 17th July. I found a possible match for an SL-14 Rocket Body (Norad No 18153) at about 23:32 BST. The direction of travel is correct & since I estimated the time rather than write it down immediately, I think this is a confirmation.