Nikodemuzz

After doing some more thinking and detective work on this subject, I have narrowed it down to two options that are price-wise within a few hundred € of each other fully accessorized: Takahashi TSA-120 with FT focuser Long pedigree and reputation for excellent quality Compact size and light weight (6.7kg, assuming without rings) Air spaced Readily available CFF 135 F6.7 Generally highly recommended on CN, but there are also some scathing reviews. Interestingly, being a European maker, is less mentioned on SGL. 15mm aperture increase, focal length essentially the same Heavier than the TSA, but still quite light for the aperture (10kg with rings) Oil spaced Lead time of roughly a year It seems to boil down to do I want to wait for a year to get 15mm larger oil spaced scope from a "new" vendor, or get a slightly smaller one almost right away with proven quality. I'm not at all into taking gambles with this investment, which makes me gravitate towards the Tak, even though I'm tempted by the larger aperture. The wait time is not a show stopper for me, being unsure of getting what I paid for in terms of quality is.

Thank you @mackiedlm! Yeah that is true that the variation between screens is quite large. And spot on that mostly people look at the photos on mobile devices these days. I probably should adjust my monitor to account for that better.

Yes it does! I'm very excited about the night skies again! If only I had a scope with a bit more focal length, the large nebulae and Orion are not very well placed for me at the moment.

Interestingly, my phone shows the images with a hefty boost in contrast and saturation compared to my (calibrated) display. I wonder which version you see.

Thanks for the compliment! To clarify a bit, I have gathered data on a few subjects over several nights. This was the first image I thought had enough data in it to be "final".

Great Scott, with the lack of a better expletive! Thank you very much for this tutorial! I went straight away to try it, and sure enough, the signal is indeed there. Pretty laborious process though, one has to be very prudent with masking in order to keep things in control. And still, a lot of tinkering, at least for me, to get the color balance at least somehow in order. Still it is a bit pink, I think. Here's the first stab at this technique, does make quite a difference. The blue stars are a good example of the masking challenges:

First completed image for the season, and the first completed image with the ZWO ASI 071MC Pro! Taken from our backyard with the SpaceCat, using the Optolong L-Enhance filter. No calibration files besides bias (flats would be a good idea, but I don't have a good way to take them yet). Roughly 7 hours of integration time over 2 nights, 15min subs. Processed in PixInsight with finishing touches in Photoshop. Struggled again quite a bit with the background, which I suppose is not really uniform in the area anyway. Despite the L-Enhance being a multi bandpass filter, I couldn't really get more than a slightest hint of the colour from the oxygen that is also present here. Whether that is due to my inadequate processing skills, or the signal just being so faint compared to the hydrogen, I don't know. Overall I'm still very happy with the result!

Thank you, very interesting! Thanks for chiming in, Garry! Not many owners of both scopes around, I'm sure, so I value your experience! Your comments are not exactly in line with the articles, which is interesting. It is a positive indication that you haven't noticed long cool down times!

To be fair, the above consideration of mine is not valid only for the TMB130SS. I'm sure the same goes for all of the air spaced heavyweights (Esprits, TOA's etc). How about the TSA-120, being so light for its aperture?

Interesting discussion about the origins of the TMB optics (and washing machines)! I have no doubts about the quality of the optics, regardless of their source. What I am a little bit wondering about is the cool-down time. I read two articles about the TMB 130SS, and both mentioned slow cooling. First, here: http://articles.adsabs.harvard.edu//full/2008JRASC.102...77S/0000077.000.html "First tests were done in September when the temperature was still around 5C. Smaller and lighter refractors would have been serviceable within half an hour, but these relatively massive refractors took some time to lose the last of the tube currents and surface turbulence...The TMB also seemed totake longer than the AP to reach equilibrium in these milder conditions...The acclimation time from a cool room temperature of 15C down to an outdoor temperature of -15C took far longer than expected. Both refractors were not totally acclimated even after 1.5 hours, although the AP was giving acceptable views by that time. The TMB did not show any detail at this point..." And here: https://www.cloudynights.com/articles/cat/cn-reports/telescope-reports/cn-report-tmb-130-signature-series-r1634 "There were some minor cool down issues. One winter session, as the temps kept falling, it never did equalize. That's somewhat to be expected with that huge mass of glass up in front. Even though the cell is designed to be temperature compensating, it's just not capable of keeping everything perfect through the most extreme temps." Take yesterday for example. It was overcast most of the afternoon and evening, -10C. During the night the sky cleared and the temperature dropped to -25C in a couple of hours. By morning the clouds were back, and the thermometer was at -20C. I would say that for midwinter this is pretty typical scenario. Autumn/spring it is similar but the evening temp might be 15C, dropping close to 0C in the night. I wonder if a slow cooling air-spaced scope is capable of following the ambient temperature, in other words, be usable for the majority of the nights. Then there is the thermal shock risk with the oil spaced scopes. Would it be enough of a precaution to use the flight case as a buffer, bringing the scope in and out inside the case? This would prevent the scope from ever experiencing the full thermal shock.

Thanks for the tip! TMB's reputation is right up there. They don't come up so much in discussions, but probably because they haven't been produced in a while and are pretty rare.

Thanks for the link, very interesting! I can easily see scenarios where a thermal shock might be hard to avoid. I wouldn't want to ruin an expensive telescope because leaving it outside after a session is not an option. This might become a deciding factor if the risk of damage is significant. Thanks for the input, Adam! It would be interesting to know in a bit more detail why the TSA-120 would be your choice!

I dom't think that there is a justification in the optics or the design, but I would be happy to be corrected on that. I think it's just that Skywatcher et. al. can produce these thing in large enough quantities to drive their prices down. Even Takahashi production is large scale compared to AP or TEC, I imagine. There is probably a decent amount of steps and time that go into making a reducer when it's done by a person, so there we go. Often I like to support the craftsmen and small producers, in this case I don't have the coin for that, at least if buying new.

Thanks for the input, Gerry! Good to hear your experiences, I know you enjoy an even colder climate than mine. What makes you say that the cold temps are especially hard on oil spaced designs? Is it because of the oil is squeezed between the elements as the lens cell contracts in the cold? Air is compressed but oil won't, causing stress?

It's pretty nuts, isn't it. Suddenly the Takahashi accessories seem reasonably priced, even cheap! 😃 I believe this is the one that is usually recommended with the TEC140: https://www.baader-planetarium.com/en/072x-telekompressor-korrektor-für-tec-140160180.html I don't know if it's the only reducer you can use with the TEC, maybe an owner could inform us on that. Of course you don't NEED the reducer, but it would be nice to have. The dedicated flattener is not exactly cheap either, at 900€. I'm sure the quality is there, though.

One thing I started to think about is thermal performance. Living here in the North means that the scope will have to be able to withstand -30C and lower temperatures without pinched optics or mechanical issues. I keep my equipment in a room that is typically a few degrees above 0C, so not quite room temperature but not ambient either. If a scope cools very slowly and the temperatures are plummeting outside, will it ever reach thermal equilibrium? What sort of differences should I expect between the Esprits and the Taks in this regard? I have understood that all in all oil-spaced solutions cool faster than air-spaced. Oil spaced would mean TEC, CFF, or some Astro-Physics scopes. Are there others within the context of my criteria?

As many have said already: it's not the weather, it's the clothing. Dress accordingly and you'll be fine. Even better if you can pop inside to warm up momentarily. Here (63 degrees latitude) it's pretty much the name of the game that when it's dark and clear enough to see stars, it's also cold. A bit cold, very cold, it varies, but cold anyway. One can prepare and be relatively comfortable by wearing layers, moving around, and drinking something hot. But it is not a coincidence that I dream of living in some place a bit warmer... Besides yourself getting cold, your equipment will start doing funny things too. Cables become rods, smooth focusers become immovable objects and so on. Wonder if the front lens has frost on it? Take a look, see that it doesn't and promptly breath it into impenetrable frozen fog. You are done for the night, unless you have proper dew bands. Ask me how I know. 😃 My first imaging experience was a good example of how the cold can throw some spanners into the works. Despite the setbacks and poor results, it was a fun night which I will remember for a long time. I guess that would be my main take away: put on some clothes, get out there and enjoy!

Much appreciated, thank you! I might well be in need of such assistance sooner than later.

Haha, indeed! The next task I would like to fulfill is to make monthly calendars, where I have my scope/camera combinations and tiers 1,2,3,4, for example. The idea is to check from the master target list, which of the targets recognized for each scope/camera combination land in which tier in each month (if any tier). To make the table easier I would like to print the results into a single cell instead of a table. Meaning that all targets that are tier 1 for scope/camera 1 in January, would be printed in a single cell. Then tier 2 and so on. Now I KNOW this would be so much easier to accomplish with VBA. I can already see it won't be as easy as I perhaps thought using just functions as I'm used to. But when it comes to actually doing the bit in VBA, well, you might as well ask me to write a poem in Japanese. I know I can learn to do it, but it will take "some" time.

There it is again, the mysterious combination of letters, VBA... I know you are both right. I can see how I can do the things I'm planning to do without that much effort, once. However, changing things later on will snowball into being a real job real quick. For example, adding or removing telescopes or cameras. This would probably be a good project to practice on, but let's see if I have enough steam to develop it further when it works. It would be good for me in the long run, too! A bit like fish liver oil as a child! 😃

I have a question for you, friends! Excel has a limitation of array formulas in a worksheet (around 65000). With the way I am approaching this tool, this technical limitation also presents a limit on the amount of objects I can include in the catalogue. With this limitation taken into account, I can have at maximum around 4000 targets included. Granted, this is still quite a bit of targets, but I would like to make sure I don't exclude potentially interesting targets. The question is, how to determine which to leave out? The NGC and IC catalogues have a combined amount of 13958 targets. Here's how I would approach the problem: Lets's remove the easy ones first: - Targets with no reported size, these won't work with the tool anyway (1411 objects) - Targets that are categorized as duplicates between IC and NGC catalogues (703 objects) - Targets that are categorized as Star(s), as presumably uninteresting imaging targets (97 objects) After these we still have around 12 thousand objects left. Here comes a bit of a dilemma. We could just eliminate enough targets, starting from smallest. After all, around 11 thousand of the objects are smaller than M57, for example. On the other hand, especially the larger, more interesting end of the catalogue is quite populated with open clusters (although there are less than a thousand of them), which apart from a few exceptions are not very interesting imaging targets. Perhaps they are underappreciated, but they are not at the top of my list, I can admit. Clearing the open clusters would clear the way for more interesting targets? What do you think?

Thank you for the help, this puzzle has now been solved! The calculation works, and referencing a few objects in Stellarium, seems to produce correct results. The working formula was: =MAX(IF(ISNUMBER('Sidereal times'!$B$3:$B$26);DEGREES(ASIN(SIN(RADIANS(P2))*SIN(RADIANS(Variables!$B$3))+COS(RADIANS(P2))*COS(RADIANS(Variables!$B$3))*COS(RADIANS('Sidereal times'!$B$3:$B$26-Catalogue!K2))));"")) I realized this IF function was not necessary to begin with: =IF(('Sidereal times'!$B$3:$B$26-Catalogue!K2)<0,('Sidereal times'!$B$3:$B$26-Catalogue!K2)+360,('Sidereal times'!$B$3:$B$26-Catalogue!K2)) It was meant to ensure that the COS has has always a positive value to process, but it makes no difference. So we can leave that out. I wonder why I put it there in the first place. Now the next (and probably at this point the last) step is to create the monthly target lists!

You can find the file here: https://www.dropbox.com/s/c3smzemb8zsb08u/astrocatalogue.xls?dl=0 The calculation I'm struggling with can be found in the AE column in the Catalogue sheet.

Thanks for the help! I'll look into these tomorrow, my brain has already punched out for the day.

Your function might work, thank you! However, if I leave the "ignore" part blank, those cells produce a 0. That results in the COS part of the formula to be zero, but the SIN part will be calculated, which could in some cases give false results. It would be better if those cells were omitted altogether, but I don't know if that can be accomplished. Sure, although I dread the amount of shame the presentation of my unfinished work will bring... But hey, open source and all that! I'll have to get back to the computer to do that, should be able to do that in the evening. Thanks, that explains why I wasn't able to differentiate the cells with those functions. Counting the cells was not the end goal, though. It was to exclude the blank cells from the calculation. I was using the counting functions to study why the logical functions were not working as intended.