Giles_B

+1 for dust in the wedge - I noticed my wedge smoking during a session a month ago, que big panic, but the wedge turned out to mildly warm on the outer surface of the heatsink - so I assumed there had just been a piece of debris - perhaps a seed or even an unfortunate insect, that had wafted into the wedge. I guess if something more substantial had entered the wedge it may have produced heat such as the OP describes.

I'm thinking of ditching the "coat over the head" method of solar observing and buying (or crafting) some specific equipment to keep myself in shade. There seem to be two options, either a cover that goes over me and the telescope like this: https://www.rothervalleyoptics.co.uk/telegizmos-solar-observing-hood.html, or a shield that attaches to the telescope, or eyepiece as in this example: https://astrospares.co.uk/products/baader-solarprotection-shield 

Of course, these things are all pretty simple, so I'd consider a DIY option, but it would need to be more sophisticated than hiding under my coat! NB I have both white light and Ha working in parallel (on a Sky-Tee), so I'll probably need any "shield" option to be x 2.

Has anyone got experience of either or both designs, and if so, which do you think is the better option?

I agree an 8" Dob is a good choice. If your only worry is that Dobs can be bulky then all you need to do is shop around as this is not always the case.

Most dobs come with a laminated MDF base, and so the material is intrinsically heavy. That said, I've owned a 10" Orion Intelliscope it was not unmanageable, so I'd imagine you wouldn't have a big problem with an 8". There are some, like my current Orion Optics (UK) Dobs, with a base that is a tad lighter and much portable (although the base, made of steel in this case, always needs to be heavy enough to stop the telescope from tipping) - but admittedly this is probably beyond the budget you suggest. There are others, though, where the MDF base design is a bit more thoughtful - like the Bresser Dobsonians - and these may hit the sweet spot for you.

Rather than go on my rather patchy knowledge of what is available, just make sure you have a good conversation with the telescope retailer making clear you want a big aperture but one of your main criteria is that the base is lighter and more portable.

3 hours ago, Davesellars said:

Just finished for the night - 7 hour session!  

If only I hadn't had work - I managed three hours then stopped at midnight. The sky was absolutely crystal clear over Bristol - ranks with some of the best seeing I've experienced in the city. Most of my time spent on the Saturn, with a huge amount of detail visible in the rings. Just amazing. Came out again at 6am to walk the dog, and  still crystal clear. If only it hadn't been a work night!

"If you have a finder scope, remove it, or make a similar filter for the finder's objective as well."

Thanks to @Gfamily for reminding me of this important point in his answer to a another post about solar filters in the beginners forum today.

Solar film over the aperture is what you need, in order to filter all the light before it hits your primary mirror - a sheet of film will fit within your budget. You can buy premade aperture filters, but this is probably a bit beyond your budget. Using some solar film and crafting your own filter is possible without too much effort - just make sure the film is well secured to the aperture. The film is extremely safe, but obviously if the film is poorly secured and slips ... your telescope, eyepiece and probably your eyesight (if you are at the eyepiece at the time) is at stake - so make sure you double check before each session, and you will overcome any risk. And DO make sure you point the aperture down at the end of the session - I almost smoked (literally) my 130mm reflector while packing up by carelessly removing the aperture filter while it was still taking some of the glare of the sun - luckily the smell of the cheap plastic focuser singeing was enough to alert me - but the lesson was well learned: the sun is a powerful energy source and needs to be treated with respect!

There is nothing you can safely do at the eyepiece end. You will find "solar filters" for screwing to eyepieces but these are NOT safe - this is especially true of a large newtonian like yours, as pointing it at the sun without an aperture filter will certainly crack the glass in the eyepiece filter, crack the eyepiece - assuming it hasn't fried your primary and secondary first.

You may also want to rig up a solar finder, or buy one - it can be surprisingly tricky to find the sun.

You will probably find that a 200mm reflector won't give the best views - the seeing during the day is poorer and the optimum is about 100mm of aperture or less. Ultimately a refractor is the way to go if you get more serious. However, solar film will give you a good taster of the joys of solar observation, so I'd really encourage giving it a spin!

Great idea - I never cease to be amazed at the adaptability of Lego - Lego seems particularly likely to be useful for testing the Baader LaserColli mk2, which is a really awkward shape.

Now as for the uses for a bottle or two of wine....

@Astro_Dad thanks, really I should have contacted Celestron myself. I think I'll give it a try with some cotton wool and detergent, I agree that alcohol based cleaners feel a bit dangerous. I guess if I can't get the mirror cleaned with detergent I'll think about something stronger.

+1 for the Baader from me (mine has held collimation well even after a drop to the floor) however I have two caveats:

1) any 1.25" collimating device in a 2" focuser will suffer from the imprecise alignment of the 2"->1.25" reducer. I found my collimation got a lot more precise with a Howie Glatter Parallizer https://www.firstlightoptics.com/adapters/howie-glatter-t-adapter-parallizer.html - but given these now cost almost £90, you may want to get a collimator with 2" capability in the first place.

2) I'd recommend at least having a collimating cap, and more usefully a Cheshire as backup. That way you can routinely check the laser has led to spot on collimation, check the secondary is correctly positioned and so forth. Often when I've asked for advice on forums about this or that issue, the first advice is to check collimation - having two (or more!) tools gives me greater confidence that the collimation is okay.

Thank you for that really comprehensive answer!

Thank-you both, for all of these answers. @vlaiv - I particularly appreciate your identifying and linking to the relevant calculators. Certainly the ball-park figures suggest I would have the room to use the artificial star, but I appreciate the help with the maths!

One thing both of your answers have made me realise is that there is a difference between using the artificial star for star testing and collimation. My understanding is that star testing is used as a final 'acid' test of collimation - that an out of focus star will show a pattern in the airy disk that indicates optical aberrations associated with miscollimation as well as other optical defects. What I don't fully understand in your answers is how I would use an artificial star to check collimation without doing a star test - could anyone explain?

I'm considering buying an artificial star to further assist collimation of my f4,8 10" Dob - I find tracking a real star a bit tricky with a Dobsonian. However, although I travel to more open locations from time to time, a lot of my observing is done in my garden, and I am not sure if I have the necessary distance in my garden to focus on an artificial star - does anyone have any practical experience?

I realise not all artificial stars created equally, so really want a rough indication of the distance needed for a 20-50 micron unit.

I'm guessing this thread gets the attention of many Dobsonian owners who are using a modded starsense explorer unit, as well as straight up users of the celestron dob, so with that in mind I have a more general query.

I had a mildly frustrating night last night because the star sense adaptor (I.e. the phone plus holder and mirror) was slow or sometimes unable to plate solve. This tended to be in brighter areas of the sky, but I emphasise it was a dark night at a Bortle 4 location - it has plate solved in brighter conditions in the past.

Obviously this needs to be replicated to show if there is a genuine issue, but I did have a good look at the mirror on the adaptor this morning - it is pretty filthy, with plenty of stuck dots of pollen and dust. I haven't cleaned it in the 2+ years since I bought it. Has anyone cleaned the mirror?

I ask because the technicalities of cleaning a small, glued mirror on the star sense are clearly a bit different to cleaning a primary mirror. I'm guessing the mirror on the star sense adaptor has no protective coatings that I could damage, plus i don't want to soak the mirror in water and end up rusting the fixings or softening the glue, so I'm wondering if Baader cleaning fluid might be okay?

Apologies if this is a bit off the wall, but is there any dust in the usb port? This is the most common reason I've had usb devices fail to detect on my PC. Usually a small amount of dust gets compacted inside the port, that needs a dig around with the wire from a paperclip to remove it.

On 02/08/2022 at 17:22, globular said:

Please report back how you get on... be interesting to hear.

Okay - here's the full report. Actually I didn't prepare and use the off-axis mask until Sunday, but it is interesting to compare the two days

I was out on both Saturday 2-4am and Sunday 2-4am (on Sunday I'd planned to observe sooner when Saturn was higher but I overslept *sigh*)

Saturday, Saturn was somewhat low. I could get good magnification down to about 6mm, but lower than that there was too much wobble. Saturn was pretty unvarigated white disk and ring, perhaps a hint of banding but very faint. Once again I found it impossible to make out the Cassini division, which has been one of my main gripes with my observations. I tried a neutral density filter, which made things darker, but didn't help much. Then, reminded of something I thought I had read about, I tried a UV/IR blocking filter. This was a revelation, cleaning up the wobble, allowing me to advance the zoom eyepiece a stop down to 5mm (but no further) and for my first time giving me a clear difference in the banding of the inner and outer ring - although I couldn't make out a clear black line between the two. Anyway I was happy that I had seen the Cassini division at long last 😃 - I eventually stopped observing when I lost sight of Saturn behind a tree.

I turned to Jupiter - much higher in the sky than Saturn - and was amazed I could take the magnification down to a full 3mm and still see a well defined disk with clear banding and - to my delight - the shadow of Europa in transit. In all I spent about 30 minutes looking at Jupiter, and 90 on Saturn, before calling it a night.

All in all very successful, so I was full of enthusiasm to try again with a stopped down scope. I fashioned a mask with a 3.5" aperture - maybe a little small in retrospect - and once again got Saturn in my sights. The seeing was, if anything, a bit poorer than the night before, and the UV/IR filter produced a less dramatic effect, although again I could make out faint banding and differentiate the inner and outer sections of the ring. Trying the off-axis filter - I was presented with a slightly dimmer (although nevertheless quite visible) image, and no real discernable effect, except perhaps slightly fainter details. Switching to Jupiter, the effect was more pronounced dimmness and fainter details.

On 03/08/2022 at 13:15, Alkaid said:

For planets, the image scale of the 10" F5 dob vs a 4" F11 refractor is about the same.   1270mm focal length as opposed to 1100mm focal length.  Not much in it, so comparing the same eyepiece between the two scopes would result in a planetary image of about the same size.  You should however get more detail with the dob due to it's distinct aperture difference.  The refractor will show less detail overall, but it shows what it can with more contrast, so it appears sharper in many cases, even if it's not actually delivering as much visual information.  

Due to living in a city, my targets are only the Moon & Planets.  From my experience, you need 4 main things for planets:   Large aperture for detail.   Long focal length for image scale.   A very stable atmosphere (rare in the UK).  A cooled telescope - make sure that the scope is cooled to outside ambient temp.    Any one of these four not conforming can cause the view to be 'off'.   Add to that the quality of the optics (mirror quality and collimation of mirrors, lenses, eyepieces, diagonals with fracs) and you soon learn that planetary observation has quite a lot of elements to it, whereby if any one of these is poor, so will be your viewing.

But don't be put off.  Once in a while it all comes together and the views can be very good.

So my feeling is that Steve was right here - essentially I got the same viewing experience, probably slightly worse, because I'd stopped down to a 3.5" not a 4". And yes, for one night of the two the view was really good, and I went to bed tired but excited having at last seen some detail in the rings and viewed some of that wonderful transit!

Anyway, Thank-you all for the help and advice (and sorry to sneak an observation report into Scopes and whole setups!). As far as new scopes go, @rl is very, very kindly gifting me an unwanted 90mm f/8.8 Meade refractor, so I am very excited about getting a 'first frac' and trying this with some white light solar 😁

Personally I start with looking at the levels of light pollution using https://www.lightpollutionmap.info/

Then I either visit the place in the day or use google street view to work out likely sites - it should give you a good sense of the level of the horizon.

Okay, thanks - I got a bit worried for a moment! Yes, I suppose there is still some pent up expectation as I've not long moved to a 10" reflector, and even more recently used it on planets for the first time.

I think you have answered my question really, which was whether I could get a frac that would "do it all" - looks like it's a firm "no" and I should just concentrate on what is needed for solar - which is probably quite a bit cheaper (in the first instance) anyway.

By the way @globular the tip on stopping down is really appreciated - I'll try it next time I'm out (this weekend looks likely to be clear 😀)

@neil phillips Are those pictures under normal, rather than exceptional, conditions?

I'm really not getting that sort of banding on Saturn. As I don't get out that often, I assumed it was the conditions.

Feel pretty confident the 10" scope's in good collimation. Dark site DSO views are crisp, bright and generally excellent.

While the skies are cloudy I'm back to my fantasy telescope collection I'm afraid.

I understand that for really good planetary views I'd need a slow catadiotropic scope of some sort. However, I also have a burgeoning interest in solar, I wondered if there a sweet spot where a slow refractor will get me both clearer images of the planets than I have with my 10" dob, and be a good candidate for upgrading my solar viewing?

To give some background, I have a quite lovely f4.8 10" dob, and this gives me great deep sky views - even better if I can get it to some dark skies (Bortle 3-3.5), which I managed last week when on holiday. Quite mind blowing, and I should really be very content. However, it's not often that a long drive to a dark sky is feasible - there are only so many clear nights when I don't have family fun or need to be fresh the next day. DSOs from my Bortle 5-6 garden are much more accessible and good, especially on a good moonless night, but there are inherent limits to what can be seen under a these conditions. I'd also say that, while lunar views are amazing, planetary views with the dob are slightly disappointing. Planets are small even at high magnifications - and don't take the magnification well. I'm happy to take this if this is how things are, but I have been wondering if a slower telescope for planetary might fill the planet gap.

I've also been enjoying a dabble with white light solar. While recently my repurposed, aperture filtered, 130mm newt does the job, my understanding is that a refractor with a Herschel wedge would improve the contrast for white light. Futhermore, as a future project, Solar in Ha is tempting, but the entry level Ha scopes (PSTs and 50mm Lunts) seem to have very narrow angles of view and this is an evident frustration of users... If I had a larger frac for white light then this would give me a clear upgrade path that might avoid these issues, assuming I one day was wealthy enough (and remained interested enough) to get a Quark.

Window shopping for second hand refractors (I hasten to emphasise this is fantasy shopping for now), I can see there are only a few on UKABS that fit the bill i.e. are around the F11+ mark with 4"+ of aperture - for example there is an Istar 127mm f/12 R30 and a 6" F12 D&G  - These are also expensive scopes (for me) even second-hand, and I imagine that any refractor with these specs would be. Is it worth saving for something like these? Would they outperform my 10" dob on planetary? Would they be good candidates for Solar?

Help me out here - I'm a bit worried I'm just getting telescope fever and not thinking this through correctly 🤩

I assume this is still the v1.1.7.1 update that happened a month or two ago? Or have I somehow missed an update?

On 30/07/2022 at 08:52, Second Time Around said:

I suspect that, as the makers of Sky Safari were involved in the project, Starsense Explorer now contains all the objects in Sky Safari Plus.

I noticed the app is now opening with messages asking me to download Sky Safari software - this would explain why...

On 30/07/2022 at 08:36, paulastro said:

Phew, thank you, that's good.  A friend of mine has just ordered one of the non-dobs for transfer to another scope.

My app was set up for the Celestron 130mm Newtonian. When I transferred the cradle onto my VX10 I did notice that the pointing accuracy of the app improved from "roughly correct" to "flawless" when I changed the 'Scope type' to a Celestron 10" Dobsonian in the app menu - not sure if others have experienced this.

@Zeta Reticulan I've read about using a neodymium filter - I guess this is the same thing as the contrast filter? I've also invested in some coloured filters so I'll have a play soon. I'm on holiday with my 130mm Newtonian, and have clear skies coming up - although the reduced aperture will surely mean i don't have any revelationary connection with Mars, I think I'm going to continue my journey!

@A Scanner_darkly Yes, the absent cassini gap worries me too. I'm pretty sure the scope is well collimated and, while I'm not obsessively cleaning my eyepieces, I think they are pretty clean. If it's not the scope all I'm left with is the {1) location - perhaps 20 minutes out of Bristol is still too near the city heat, and this is spoiling the seeing, or, (2) Me! Maybe I just have made less progress as a visual observer than I'd like, and maybe more hours in the seat is the remedy.

Both cases lead to the same conclusion. Get out with the scope more! Look more carefully!

@Elp the Technosky Cubo  looks like great value, and is definitely a great tip. Thank you.

Thanks for the clarification on where the wobble might come from - looks like a tripod is what is needed first and foremost - indeed, the legs were retracted in an effort to get more stability, but all in vain.

I think I'm generating more confusion about the 10" newtonian, so I'll try to explain a bit: I have a second-hand OOUK VX10 which is mounted on a dobsonian base (and very good the base it is too). In the past my experience with dobsonian bases has been that it is often very hard to track planets at high magnifications. The VX10 has a dovetail so can be mounted on a tripod - indeed Orion Optics allow this customisation (but with an EQ5M mount) at point of sale. I don't need go-to, and I don't need EQ.

So I'd like this advice: what ALT-AZ mount would take this (11kg) weight, and, ideally what tripod it should be paired with.

If I should then get a new mount (for whatever OTA or reason), with this information I will know if I have an option to mount the VX10 upon it (tall ladders not withstanding - the OTA is 1200mm, so not so big).

I've just dusted off my Celestron 130AZ Newtonian and started doing a little solar observation. The scope comes with an alt-az mount and tripod, but having come back to it after many months of using a larger dob, I've noticed it gets very wobbly at high magnifications, even in still conditions - just touching the focuser gets it shaking for a good 30 seconds. I guess that a new mount and tripod might help this? Indeed, it would probably make any upgrade to a refractor (specifically for solar) less painful too.

Now, in my fantasy upgrade plan (not privy to my partner or bank manager) I'd always expected I'd want a bigger alt-az mount and tripod so I had the option of mounting my larger 10" Dob, which weights 11kgs. Alas, I've parked the idea some time ago, because it seems I'd need a £1000 HEQ5 to handle this weight, and also because my current OOUK dob base is very smooth and has largely eliminated the need for fine tracking controls.

Now I'm thinking about mounts again, I'm confused as to whether the weight limits given for EQ mounts would apply to an alt-az setup (I'm not interested in imaging, so can't imagine why I'd need an EQ mount), but there don't seem to be any "big" alt-az mounts. Why? Is the limiting factor for alt-az mere stability, rather than whether a motor can support the weight of the OTA? or is it just that there is no demand (is there some reason to go for EQ that I'm not considering)? or have I got a bit confused about the whole business? I'm guessing it's probably the latter, and would really welcome some help!

@Pixies I'm starting to get used to being seated at the dob, as you say, it definitely helps extended viewing - that said I've not invested in a dedicated and adjustable chair yet, just more or less awkwardly perching or swinging on a camping chair, so perhaps I've found something else to spend money on (*sigh*)