jetstream

I was wondering if anyone else has explored the concept of the thermal slide with regards to local thermal management? In conversation with a local astronomer 300km away the conversation swung over to local thermal management. By chance we both do similar things. Hes an imager (and vg) and Im a visual observer. Basically you observe in an area (higher) that allows the cooling evening air to "slide" down the hill taking ground heat with it, resulting in better local seeing conditions. I discovered this when clearing an area of our property and brought a scope up. The difference is significant. The preferred base for me is sand- it reflects heat in the day and cools fast at night. This is one of the ways used to squeeze out very high mag on solar system objects. I find this interesting.

Awesome!! Cant wait to get it on Saturn myself a favourite of favourites. It can take on a ''chiselled glass" appearance in some scopes and I too have seen the division under great seeing.

This makes me smile too...👍 The mouse is hovering over one..

This makes me smile 👍

If I were you Id be seeking a Tak .... your location helps... IMHO.

Well, Ive suffered a moment of weakness... Not uncommon with regard to astro equipment thats for sure. Ive found a new Pentax XO 2.5mm after a many year wait and the vendor passed it along to me at a nice price knowing that I'm a "collector" and not a re seller. I cant wait to compare it to the 2.4mm Vixen HR in the TSA120. Now that I'm able to carry the AZEQ6 again the TSA120 is seeing a lot of use including another stunning lunar session last night. Any experiences with the 2.5mm XO is great to hear. Also great to hear are thoughts about the Pentax 3.5mm and the 4mm DeLite, feel free to wander in the thread... I always do ps and now I'm sitting patiently under a spruce tree in the rain for the 5mm XO to wander by lol ( a reference to former hunting lol, glad I gave that nonsense up)

Its the rate of cooling of the lens vs everything else that determines the currents. The slower cooling tubes degrade the image longer but this depends on the rate of cooling between the lens assy and everything else. IMHO. There is no free lunch- unless the lens is equalized with everything the image is degraded IMHO.

Any tube can have tube currents. It is a function of the temperature difference between the lens assy and the tube itself, including the focuser etc or anything that could be a heat or cold sink. Some SCT astronomers use reflective bubble wrap to "slow down" cooling of the tube to more closely match the cooling rate of the big corrector plate etc. My truss dobs can have "tube currents" from the shroud closed and I adjust it for the most stable views, among other things done. I hope the OP can garner some useful information from this thread in his future telescope choice.

Kudos to you Olly👍 I respect your integrity. Gerry

Amen to that.

@ollypenrice Your voice of experience is a much valued asset to us. Ive heard about issues with the Tak FSQ which highlights the need not only to research the brand but also models within the brand- any brand. IMHO. I think I remember Tak having a coating issue years ago too. My hat is off to you for reporting the FSQ issue you have, many if not most scope owners will not post about issues with their scopes as it can effect resale. It sure helps people to know about the probability of getting a good telescope through these disclosures. Gerry

Great point and I must add a carbon fibre tube takes longer to acclimate.I chose CF for the 90mm because of all the abuse it would take on dark site trips and extreme temp differences. It has been "thrown" in the truck, no dents obviously and CF will not move around like an aluminum tube in wild temp swings. A well designed aluminum tube and cell wont impact views in extreme temps ie the TSA120. Its a crap shoot if the SW120ED will have a successful cooldown from 21c to -30c. The cell pinches more than 50% of the time, making it unuseable for a session then. There is no question air spaced triplets take a fair bit of time to cooldown IMHO. Eventhough my TSA is stored in a seacan, I still give it time to settle down, maybe this is just me. But the views speak for themselves..

My recent interest in DPAC has me reading tests already done. One test set in particular, from another site and from a few years ago showed a TEC 140FL with the fringes curved up in red and blue, green was ok. The TEC140ED tested was better corrected. How can this be? If that 140FL had been another brand the wolves would have been out, but because it was a TEC the comments were like " well its still a great scope" or "I'll take it off your hands lol" etc. I dont believe in "mythical" scopes, just ones proven to give great views, and these ones will test well. All this just an opinion.

@Kobayashi Maru Just had a stunning lunar session with the TSA120, seeing was pretty good allowing up to 375x, however most views were just under 300x. My 15" dob is a vg planetary scope but had thermal issues and the aperture was a bit much for the seeing. I see you have a 10" dob- great scope- a 100mm frac will compliment it well. One thing- Ive noticed that the 120mm is more sensitive to mediocre seeing than the 90mm. Not sure how your seeing is where your located but if your seeing isnt good or better most of the time a 100mm would be the better choice IMHO. Let us know what you decide to get 👍

Rumour around the campfire is the the earlier Sw120ED's labelled "Pro" had some excellent optics. Mine goes 300x on lunar, about 265x on Jupiter. Its not bad ...until you look through something with truly good optics- and I'm fussy. The 120mm's definitely need a heavier mount system, the 100's do not IMHO. I bought a moonlight focuser for it eventhough I had the stock one working not too bad.

It can be... depending on the optics. The very highly regarded Tak 100mm doublets are excellent visual telescopes, however some other doublets might not fare too well and be subject to sample to sample variation IMHO. Mind you its possible to get a "good one" . Maybe most are good, I dont know. I do know that when you buy a Tak what I see in mine you will see in yours. My TSA120 is a superb telescope, my SW120ED doublet average. My older 90mm Stellarvue triplet is a vg scope but not in Tak territory contrast wise on the moon and planets. Its said that refractors by nature are small telescopes, always will be small telescopes, regardless of aperture so it makes sense to buy the best you can afford. If I had a choice in refractors and could spend on a 120mm triplet or get a 100mm Tak doublet for the same price, Id go for the Tak doublet. Gerry

The TSA120 is a nice scope.

Ok, I think I'm ready to give up the ice and snow and move there Magnus! Great luck tonight!

Mine is excellent, thankfully.

Thanks for the excellent reply Don. What was the issue with the 3.4mm Hr's ? Mine works very well.

They are excellent for binoviewing IMHO. I use the 32mm, 25mm in the Binotron 27's with the powerswitch. I also use the Tak 18mm, 12.5mm othos and like the extra bit of eye relief they give over plossls in this range.

Great dog!!

It does, kind of. Because of binocular summation and what this allows the brain to do things can be "averaged out" IMHO or definition actually increased as you say later on. This and the "false exit pupil theory" that come with binoviewing are an interest of mine.

👍 Contrast transfer at a larger aperture. The TSA120 also has excellent contrast transfer, to my eyes. Ive seen good eyepieces "dull" the transfer while others do not, depending on a few factors.

What I like to see is "secondary detail" ie not just Jupiters bands but the sharp tonal differences in them. The 15" will bring out very fine edges in the bands and in much earlier reports called them "riffles". The TSA is also excellent for its aperture. I have no doubt that this is due in part to the 15" (and your Mewlons) higher spacial frequency and the high quality optics that allow the contrast transfer to happen. I also find the eyepieces do matter and the interaction between them, the scope and the individual.