Piero

Yes, I hold it with my hand and use it for star hopping. I've also downloaded Alvin's Herschel 400 guides (3 vols) on this tablet. That should be a lot of fun and within the limits of this dobson. Glad to hear that your new encoders are working well with your 15". The Zeiss zoom is one of my main blocker from getting a paracorr2. I love that eyepiece, but I suspect that the fact that it is not fully parfocal across the zoom range, could affect the setting of the paracorr2. Also, when you said that the paracorr2 sharpened the views of your Delos eyepieces, do you mean on axis?

Turn left at Orion was one of the first books I bought. Although there is some valuable information, I never managed to take it to the field.. So.. yeah, I rarely use that book. Do you also use U2k Guide?

It's excellent! This is also well made and free. Said this, it's a bit like Uranometria: very strong on DSO (e.g. galaxies), but a bit poor in terms on labelling and double stars. I've read very positive comments on those three volumes.

I have a TV60, which is quite similar in specs. With it, I want a 24mm, 9mm, and then 3.5. Al Nagler suggested: 24 Pan, 9mm Nagler, and TV Nagler zoom. I completely agree with him on this. I have 24 Pan, Nikon MC1 zoom 21_9mm, and Vixen HR 3.4mm and 2.4mm.

As I said before.. I am going to stick with my trusty APM UFF 30mm..

If you also want the description of the objects you observe, then I'd suggest to also get Burnham's celestial handbook in the second hand market.

That's a stunning image! I was observing that area too a couple of days ago.

Last week, when the moon was not out, I was star hopping the Plaskett's star in a field down to 14 mag. Not that I needed to go so deep, but I wanted to make sure I was identifying it. I found sky safari quite accurate, particularly after aligning it to the telescope axis. I have the Pro version, but the Plus version would probably be fine too. If one needs deeper DSO, she or he can always download extra data. The current database is already huge though, probably on par with sky commander. You are correct though, very low temperature can affect the performance of a tablet battery and possibly screen. So, under your extreme conditions, your solution might be the only one. Regarding the "old school", nothing wrong with that. I like to get the best of both school. Consider Burnham's celestial handbook or Sidgwick's books.. certainly old school, but, oh man, how much inspiration and thought they offer!

I have the Lunt / APM HDC 20mm. The field is well controlled up to the edge with very minor astigmatism in the last ~5% of the fov. Honestly, you need to look for it. The lens rubber is particularly comfortable. The eyepiece is quite light (678g) when compared to the Ethos 21 or ES 20mm 100 deg. In general it is a fine eyepiece. Mine does not get much used simply because 1) I prefer eyepieces with a smaller AFOV (I kind of feel lost with 100 deg), and 2) as my telescopes are medium / slow I tend to jump from 30mm to 12.5mm. p.s. Mods might complain the fact that you asked about buying / selling outside the classified. I PM'ed you, but will stick to the rules not to discuss about this here.

Yes, encoders can be very valuable. Sky Safari can go quite close though, with the main difference that it lets you star hop.

I have the S&T pocket star atlas too. For some reason though, I've never really got along with it whether indoor or outdoor. For sure I am a minority because all the comments I've read are very positive. The issues I have are: limited number of stars. Fair enough, it is a pocket star atlas, but on the other hand constellations are often in multiple pages. So it hits neither the detail, nor the broad view how pages are presented. I feel comfortable with pages following a decrease in RA. That's intuitive to me colours. Colours are fine with me indoor, not outdoor That's why I prefer the use of a tablet in the field and a rich star atlas for planning observing sessions indoor. For binoculars or other wide field observing at low power, I prefer a broader atlas than S&T PSA. For instance, the Bright Star Atlas by Tirion and Skiff works better to me. The only drawback of this atlas is that the charts does not have correct angles, which can be an issue particularly in the polar regions.

I've heard of, but never looked through them. How are they? Edit... just found this:

The telescope has consistently been working very well for a while now. Stars don't show traces of astigmatism. Last night I had another nice session. The sky was rather steady and clear, with very low humidity. The telescope cooled with the fan on for about 2h and then collimated with my 2" Glatter laser (without tuBlug). Eyepieces: 30mm APM UFF (large targets), 12.5mm Docter (all targets), Zeiss zoom (all targets). 20mm Lunt was used for the galaxies, but didn't show anything more than the Docter. Lumicon OIII was used for the Eskimo PN. Main targets were: Monoceros: M50, NGC 2264 (Christmas tree cluster), Plaskett's star (giant O-type binary SE of 13 Mon) Leo: Leo triplet, NGC 2903 (W from epsilon Leo) Gemini: M35, NGC 2158 (interesting particularly above 250x), NGC 2129, NGC 2392 (Eskimo PN - what a sight at 400-500x!), Wasat (delta Gem) Cancer: M44 (Beehive) M67 (King Cobra cluster) Canes Venatici: M51 (faint spiral, but no connection due to LP) I must say that I was impressed with all the targets I've seen. The views were really rich in colour and intensity, with "star dust" visible in the background sky. Beautiful.

[A1] If the laser beam strikes outside the centre of the silhouette on the primary mirror, the focuser axis is misaligned. Assuming that this fact is ignored and one completes with the primary mirror alignment, the result would be that the primary mirror axis is "aligned" and the focuser axis is misaligned. To my understanding, this should show something like: In this figure, the focuser seems perfectly "squared" to the secondary mirror, the primary mirror is collimated, but the focuser axial alignment is still off. One could align the focuser axis first. This would make the secondary mirror look like more elliptic. Then the primary mirror can be aligned. Would this be fine? For visual, I would say so. The secondary mirror is clearly oversized and the primary mirror is still fully visible. There are cases where this cannot be sorted so easily though. If this is the case, one could move the secondary mirror slightly away from the primary mirror and collimate the focuser by levelling the small Allen bolts to the right of the focuser. The focuser Allen bolt at the bottom right needs an extra touch. This would allow to move the reflection of the primary mirror towards the centre of the secondary mirror a bit more. [A2] The effect should be the same as with the laser.

Having a budget limit is important, but understanding your interests is even more, I'd say. Let's simplify a bit.. Imaging. This has rather different requirements. Personally, I would keep this as separate. GoTo. Are you interested in GoTo mounts because you don't like star hopping much? A 10" (solid tube) dobson is a noticeable step up from your 6" and a very good all-around. Personally, I would get the "manual" version (=no GoTo) and learn how to move around the sky. I would then add a decent collimator, Sky & Telescope Pocket Sky Atlas, and 3 decent eyepieces to cover 5-4mm, 2mm, and 1mm exit pupils (basically eyepieces with focal lengths of ~25mm, 10mm, and 5mm). I would also get an adjustable chair and an AstroZap dew / light shield. This telescope can still be moved by one person without too much effort and fits in the backseats of a car, if you want to take it out to darker skies. One day you might decide to get a second grab 'n' go telescope like a 80mm F6. This could be used for wide field imaging too if you add a GoTo mounts like a SkyWatcher HEQ5 PRO.

As I've a couple of days off this and next week, I am revising my equipment a bit, which primarily means cleaning up and check that everything is okay. This morning, I took sometime to improve my Baader VIP barlow (now barely recognisable!). In particular, I added the standard ring 2"-to-T2 (which comes with the barlow) at the bottom of the 2" Baader nosepiece. This allows me to use 2" filters at the bottom of the nosepiece and just above this ring (see photos). Some tape was added so that the cap stays in place. This also facilitates the removal of the end component when the filter is added. This can be very handy for planetary nebulae with my Zeiss zoom. With the VIP, the zoom operates in the ranges of 142.20x to 532.74x and 159.13x to 596.16x, with 1x or 2x 15mm spacers respectively.

I had 1.25" Astronomik UHC and OIII filters but these were replaced by 2" DGM NPB and Lumicon OIII. No direct comparison was done between the NPB and the Astronomik UHC. Both are very fine. I prefer the NPB for the reasons stated by John.

Yesterday I received a copy of interstellarum deep sky atlas (IDSA) so that I can visualise the location of the objects described by Burnham in his celestial handbook. I find this approach incredibly useful to learn more about the sky. This wasn't new to me, but when I was doing so, it was with my TV60 which is a bit limited in aperture. With the dobson, it's another story. Looking forward to start off making a good observing list for monoceros, one of my favourite constellation. Outdoor, I prefer a tablet with sky safari to a paper star atlas. The IDSA is a great and powerful tool, but in my opinion it is more suitable indoor for studying the sky. If I really wanted a paper sky atlas for outdoor, I would use Uranometria 2K AFTER a list of targets indoor was created indoor using another atlas. Both atlases complement each other in my opinion. IDSA is great for understanding what is visible and what is not given a certain telescope. The labelling is also great, particularly for double stars. U2K is great because is more readable in the dark as it is black and white and the fonts are reasonably large for all kind of targets. It might also be easier to handle on one's legs if observing in a seated position. Said this, I prefer a tablet with red screens to dim the brightness in the field. To me this is far more practical and allows me to make paths between faint stars, which can be tricky in areas of the sky without bright references.

Good luck with the restoration of this Dobson. Hopefully it will see some light soon!

I also think that it is a good companion to Suiter's. Same for Texereau's how to make a telescope. Same for Burnham's. 👍

I bought a copy of IDSA, in order to map the objects described in Burnham's celestial handbook and create observing lists. The atlas for outdoor work is Sky Safari Pro instead.

Star names - their lore and meaning by R.H. Allen is a classic one. It is mentioned quite a lot by Burnham in his Celestial Handbook, which is another classic. Both are highly recommended.

Sidgwick's Amateur astronomer's book is excellent in my opinion. Very inspirational and rich of insights. A keeper.

Thanks. Burnham cites that book quite often. That's how I became aware of it.

Found in the second hand market: