alex_stars
-
Posts
223 -
Joined
-
Last visited
Content Type
Profiles
Forums
Gallery
Events
Blogs
Posts posted by alex_stars
-
-
On 24/09/2021 at 00:12, John said:
Just managed to get Neptune's moon Triton with the 130. Rather pleased with that - it's mag 13.4 dimmed to 13.7 by atmospheric extinction according to Stellarium but the limit for 130mm aperture seems to be 13.4 according to the calculators
I've no doubts that I've picked up Triton visually and it's position corresponds with Stellarium and Cartes du Ciel. Needed lots of magnification - 400x and even 600x used (crazy !!!).
Perhaps Stellarium's estimate of dimming is too pessimistic ?
Anyway, nice to spot Triton with the 5.1 inch scope
Hi all,
@John, I am very intrigued by this observation and want to attempt to do the same with my 125mm Apo. I was wondering what you used to get to such high magnifications. Guess you used a barlow? If so which one did work for you.
Another question I had on the Oval BA. Did anybody already figure out how to find transit times on it. Even though Jupiter season is coming to an end at my location I want to get ready to observe it next time round.
Best wishes,
Alex
-
Hi all,
just wanted to join the conversation now as I am in a somewhat similar situation as @Surfer Chris. I own a TS 125 Doublet on an AVX mount (we discussed the merits of that scope here). It is a fantastic scope for visual planetary. However I can't/don't want to leave the scope permanently mounted outside and it is too heavy to carry indoors on the mount and tripod. So I also think about a small grab and go setup to just carry outside as I at times set up the 125 in the evening and end up not observing long due to bad seeing conditions.
Now I wish I could just order one of these Taks, and if my budget would allow, I would go for the FC-76Q as mentioned above. However that is simply not my price range and I just can't afford such scopes. However as mentioned, I am more then happy with my TS 125 and I don't crave for any optical quality upgrade on that, So I tell myself there must be a more affordable solution for the "grab and go" setup than a:
41 minutes ago, JeremyS said:Berlebach Report + ScopeTech Zero head + either Tak series series or FC76
Hmm. I currently contemplate the initially mentioned Skywatcher 72/420 ED-Apo on a AZ-Pronto, or the little brother of my TS 125, which would be the TS 72/432 Doublet. Another one would be the TS 80/560 Doublet, which has a bit longer FL and is still at 3 kg.
Just mention those and wonder if anybody has some experience with those. Maybe there are more people like me for whom a Tak is just a bit outside their price range.
The FC 76Q with its f/12.6 would be of course perfect for planetary, but I guess a good f/7 Apo should be just fine too as a grab and go.
Thoughts and comments very welcome.
-
1
-
-
Jupiter looked so serious that night
here my late entry as I only now got the time to process the data. Below some processing details for the image:
- 5 time 10,000 frames captured on August 13th, 2021 between 22:02 and 22:15 UTC. Not evenly spaced as recording midpoint times indicate: 22:02, 22:05, 22:10, 22:13, 22:15.
- Captured with my 125 mm TS APO, a Baader 2.25x Barlow and an ASI 290 MM. Used a Baader R-CCD Filter so this is R-Band only. Captured with FireCapture.
- Processed each frame set the same way with Planetary System Stacker and used only the best 10% of each frame set for stacking
- Animation was done in Gimp but no further post-processing, so each frame in the final animation is as it comes out of the processing pipe-line, and its on the original image scale (about 0.3 arcsec/px according to FireCapture)
- One can nicely see the seeing conditions vary in those 13 mins, as well as the rotation, obviously.
Cheers,
Alex
-
5
-
On 16/04/2021 at 18:47, Deadlake said:
Question is can they be collimated? That's how a dealer can push the performance, or so Rupert told me in the case of the 125 mm Tecnosky doublet.
The FPL53 triplet version of TS (and Tecnosky) has a temperature compensated lens cell which can be fully collimated:
as does the FPL53 doublet I have:
The dealer I got mine from (not TS directly) told me that these TS scopes are easy to collimate and he prefers the collimation mechanism of the TS (and Tecnosky) over ES for example....
Also the new FPL55 triplet is fully adjustable:
So collimation should not be a problem on any of those.
-
1
-
-
On 25/03/2021 at 21:13, Acrab67 said:
It was bad seeing for sure. What made me wonder were the website Meteoblue seeing forecasts for my area. I do not understand how they give a forecast with a green value of 5/5, with a Jetstream greater than 30m / s, which is precisely the opposite indicator. Hence the twinkle of Sirius.
Yes, Meteoblue, which I use a lot as well, is sometimes hard to interpret. However it is important to know that the presented measures at Meteoblue are not all summed up in the seeing index numbers, which you refer to with 5/5. Have a look at the explanation on their website:
https://content.meteoblue.com/en/spatial-dimensions/air/astronomy-seeing
Basically the two seeing index numbers are based on two atmospheric models and an integration through the turbulent layers to estimate visibility through theses turbulent layers. They are not connected to the jetstream estimation, which is a different measure.
In a nutshell, all measures at meteoblue have to be "good" to indicate a really good night: all three seeing measures, the jetstream and the bad layers as well....
-
1
-
-
Hi,
I own an AVX and have successfully used it with a Skymax 127 (7 lb). That would put it down to about 23% of the maximum payload. I remember I did not slide in the counterweight all the way towards the mount, so one could possible go lower. However balancing the mount was already a bit tricky with the 7 lb payload.
-
@Captain Magenta, did you run your photos through the MTFmapper? Just curious. I still did not manage to test my new APO, however I will post as soon as I get a chance to take some test images.
-
@Acrab67 congrats on the new scope! Looking forward to read how you like it.
As @johninderby pointed out, I also have wondered how these screws could have been bent in shipping. Mine came like Johns, very very well packed and in perfect condition.
Anyhow, two screws can be changes, no problem there.
Fingers crossed for first light soon.
CS,
Alex
-
1
-
-
a yes and good luck for tonight @johninderby. Fingers crossed.
-
40 minutes ago, johninderby said:
Was reading a German report on the scope that pointed out one interesting characteristic. Apparently these doublet optics are designed to optimise the green and blue wavelengths rather than the red as the eye is least sensative to red. However this can cause minor red fringing on bright stars and reduce contrast on Mars. Testing showed that by using a prism diagonal (Baader T2) which refracts red differently to blue and green it can cancel out the differences and get rid of any red fringing and increase contrast on Mars. Apparently the light path length of the prisim is important. Not sure how noticeable this would be in the real world but interesting nonetheless. Will have to compare views of Mars with a prism diagonal and mirror diagonal to see if there is any noticeable difference. 🤔.
That's right and here is the original link: http://www.astrotreff.de/topic.asp?TOPIC_ID=230296&whichpage=4. I summed this up once (https://stargazerslounge.com/topic/371104-refractor-for-planets-mostly-visual-4-or-5/?do=findComment&comment=4031965), but basically it boils down to this:
- That's right, the 125 mm f/7.8 from TS/Tecnosky is optimized towards blue wavelength and not red.
- That is actually good news as one can correct/optimize that for visual use by adding some extra glass into the light path (like a prism or bino-viewer
- Gerd Düring (probably the guy behind Gerd-2 in the post) has calculated our doublet with correct design and glass types and came up with the optimal light-path-length to add glass to optimize the view
- If you add 65 mm you get an optimal PolyStrehl of 0.95, which is awesome
- Unfortunately there is no prism with exact 65 mm, but any added to the light path would make it better (even though it is already very good!)
-
1
-
First review from first light yesterday night which was a success.
First off, maybe a word on what is my baseline to compare. I worked a lot with a Skymax 180 the last year and had a William Optics Fluoro Star 110mm f/7 Triplet Apo for a few weeks now borrowed from a friend (to get into APO mood). The 127 mm TS/Tecnosky is a Doublet with FPL-53 / Lanthan and I don't know the glass types of the WO. All mounted on a Celestron AVX with two counterweights. All observations below were done with a TS 1.25" diagonal (99% reflection - 1/12 lambda)
Seeing was rather good early in the night and got a bit worse later on (as you will see which double stars I managed to split). Sahara dust was mostly gone from the air and it did not bother the observations.
First I took a close look at the moon, magnifications between 65x to 305x. For an overview I took my 15 mm Vixen SLV in which the moon fits nicely at 65x. What a crisp picture with high contrast, even early in the evening. Motivated by that I took a closer look with my Hyperflex Zoom/Hyperion Barlow combo. The scope took the max 305x very well and I got very good views, even though the seeing did not really allow crisp views at that magnification. I was searching for CA but did not find any signs of it, 👍. I have to be honest I did expect some, given that the scope is a Doublet, but as @johninderby pointed out, no signs of it.
Next up was Rigel. Seeing was pretty good at that point and I managed to split Rigel and its companion (about 9.4" separation) at 219x (Hyperflex/Hyperion at 10 mm). Amazing!
Then I took a look at M45 - Pleiades with my 32 mm Plössl. They fit nicely into the view at 30.5x. A beautiful view. Swing over to M42 (Orion Nebula) to test the basic Deep Sky capabilities 😀. For a 5" scope I got very satisfying views. It's not meant to be a dedicated DS scope but it has its capabilities. Now that is not my field of observations, so I stick planets and double stars.
Mars was a lovely view, small but well defined. I tested the Hyperflex/Hyperion combo as well as my SLV 6 mm. All in all very satisfying views (seeing permitted). I instantly saw the potential for planets with this scope. Looking forward to the upcoming planet season.
Back to Rigel, but the seeing got worse, no way of splitting it now. So I went for Meissa. No problem there at 163x with the 6mm SLV. This EP will be my Jupiter setup and testing at Meissa (and earlier on Mars), the views very really nice. The SLVs have a wider view that the Hyperflex, that's why I keep those as my fixed FL EPs.
Motivated by @John recent post, I went for Sirius. Unfortunately the seeing was not as good as it was when I first went for Rigel earlier so no chance of splitting the "Pup". I ramped up magnification and looked for CA. Hard to tell with the seeing conditions but maybe a hint at 305x. That is with the HYperflex/Hyperion combo. Hmm. Either way, the possible CA was sooo minor that I would not worry a second about it. I want to re-check in better seeing conditions before I would dare a definitive statement. Took the chance and checked for collimation. Spot on. As expected. So I placed my virtual "Collimation OK" sticker on the scope to keep up with @johninderby scope. Have to say though that my scope was selected for me by my trusted dealer, so no surprise there. Still very satisfying.
To close the night I though I follow @Johns suggestion and had a go at Beta Monocerotis. At 163x (SLV 6mm) a prefect split of all three stars and a very worthwhile view. Satisfying finish of the evening.
To sum it up (after one night out!):
- Very solid mechanical built, focuser and all.
- The AVX carries it nicely for visual observations. I use a second counterweight though, that's more convenient.
- Did not find any signs of CA, so I am more than happy with my new doublet and that without a prism, TS diagonal just fine. So this graph (https://stargazerslounge.com/topic/371948-how-do-i-interpret-takahashi-diagrams/?do=findComment&comment=4038693) is basically telling me my scope is awesome.
- Very sharp, high contrast views, as expected.
- Magnifications up to 305x no problem at all. Maybe I should start considering shorter FL EPs (SLV down to 2.5? well at least down to 4).
- At 125mm it has enough punch to do some DS, but I have the scope for planets and double stars.
- I already really enjoy this scope...
That's all from the first night. More to come and looking forward read @johninderby first extensive report.
-
8
-
Same here, a really nice scope I really do like from the start 😁
Clear skies for tonight's first light as well from my side
-
So it arrived in a set of nice boxes:
same scope, just from TS and no "collimation OK" sticker 🙁. But I got it from a store where I know the owner and he does check the collimation and adjusts it if needed, so it should be OK as well.
A yes and here it is outside after a daytime test on the next mountain top:
Ready for tonight.
There is some Sahara dust in the air but that should clear out until later.
First impression: I agree with @johninderby very well built, serious stock focuser, similar finish than WO. Mechanically top class! Daytime optic test compares nicely with a WO 110 mm triplet I had for comparison a week ago. Nighttime test comes hopefully tonight.
-
7
-
1
-
-
And here we go.
One box with lots of padding material
and there is another box inside that:
And in that box is another box and a foam box with:
My brand new 125 mm f/7.8 TS doublet.
Nice.
-
19
-
1
-
-
18 hours ago, johninderby said:
Very nice pictures of your new scope @johninderby I love the quality stickers of Tecnosky. Do let us know if the collimation is "ok" 😀
Fingers crossed for your first light tonight.
Mine from TS is in the delivery truck right now and should be with me within hours. Guess that makes the two of us tonight starring through such a nice scope!
If you don't mind then I will post some pics of the TS version here as well.
-
2
-
-
I agree, the 115 F/7 triplet has a very good reputation. I have been shopping for a refactor recently as well and my top contenders were the 115 f/7 triplet and the 125 f/7.8 doublet. I took the doublet as I am mostly observe planets visually.
However I had a long telephone call with TS and a nice discussion with their tech staff, the triplet has very good color correction. Another upside is that TS actually tests (star test presumably) and collimates this triplet before shipping on their optical bench, so that is a nice service to get for free.
Regarding astroshop.eu. I have been doing business with them and their service is equal to TS and the other shops. However when you order the 115 mm from astroshop.eu you will get the Italian branded Tecnosky. It is the same scope, however they will not test and collimate the triplet. As far as I could find out they will order it from the Italian supplier and forward the shipment to you.
Here is the link of the Italian supplier directly: https://www.tecnosky.eu/index.php/prodotti/telescopi-e-ota/apocromatici-ota/rifrattore-apotripletto-115-800-v2.html
Tecnosky did an interferogram test on one of those and the Strehl ratio comes in at 0.978 which is really good for that price point
So double 👍 for that triplet.
-
2
-
1
-
-
I have added another two measures to the graph, the MTF20 and MTF10:
- At MTF10: the human eye can not resolve contrast anymore and camera noise even of good cameras is a serious issue. So we can use MTF10 as the real limit of what we can observe, both visually or with imaging. Note that the Dawes' limit is at higher frequencies but that is very theoretical. MTF10 is close to the Rayleigh Limit, which we should use to stay realistic.
- At MTF20: most human eyes can't perceive higher resolutions. If you think you can, well, go check if you can see the resolution limit of the screen on which you read those words. Most digital screens are designed to the MTF20 limit of the average human eye. I know I can't observe below MTF20. We could use MTF20 as a practical observation limit when working visually.
For me the MTF20 limit puts scopes into a nice perspective.
Here also some further reading links for the interested:
-
How to read MTF curves (recommended!)
-
Kind of don't want to let this thread die, so here is the long ago mentioned comparison between a C14 (planetary imaging favourite) and that 7 inch Mak.
Couple of things to take away from that graph. And I am sure if people have been reading until here, they can interpret the MTF graph as well. However one measure we did not mention in the discussion yet is the
MTF50 value: which is the spatial frequency at which the MTF of a given system decreased from 1 to 0.5 (horizontal dotted line) Below the MTF50 we definitely perceive a quality loss and this measure is often used for lenses when comparing.
- The advertised 7 inch Mak (actually 6.77 inch) is "equal" in transferring "contrast" with a 5 inch (actually 4.53 inch) unobstructed refractor. That's what we often read on the forum. You see it in the graph where the green and red line overlap perfectly. Note that the MTF50 value for both scopes is the same a 0.42/arcsec or at 2.38 arcsecs.
- A C14 is equal to a 248 mm (9.76 inch) refractor and the MTF50 value for both scopes is at 0.91/arcsec or at 1.09 arcsec.
- Hence we can argue that a C14 is really good until the average seeing limit (say at 1 arcsec) whereas the 7 inch Mak only is as good until say 2.4 arcsec. This is in line with the experience people have with such scopes.
- For us astronomers the question arises, how far to the right of the graph can we go, because that is the question on what scope to get.
- To spark a discussion, I plotted the 0.4 arcsec mark, which is the best seeing on the planet and I wonder if the C14 would be good enough to work to the full potential of such places.
- We could also turn the question and ask at which MTF value do we need to draw our line?
Looking forward to the next round of comments
-
1
-
My favourite Barlow is the
- it goes right into the Hyperion and Morpheus EPs
- fits any other 1.25" EP with its small adapter (fits nicely onto the Hyperflex zoom as a screw-on Barlow, even though the EP gets rather long)
- and has a T2 adapter, which is perfect for imaging. There you can get crazy with T2 extensions and get all kinds of magnifications. I use a 40 mm T2 extension regularly for imaging.
-
A yes, it gets better. The newest version of MTFmapper can do:
how nice is that for us refractor people 🥳
I can't wait to see all the comparison discussions on the forum
-
A yes, regarding the target chart distance for MTFmapper
One should place it at a distance so that it covers the whole sensor. As an example for my scope and setup (just if people are uncertain about the math):
- I soon gonna have a 975 mm FL scope
- I have a ASI 224 MC
- This results in a FOV for my sensor of 0.29° x 0.21° (just use astronomy tools in imaging mode 😀)
- Now if I print my test sheet on an A4 paper (297x210 mm) I can work out the distance
- Lets focus on the long edge of the sensor and the A4 sheet (so we have 0.29° for 0.297 m)
-
The distance to target is distance = 0.297/tan(0.29°) which is 58.67 m (just make sure you either convert to radians or use a tan function suitable for degrees) I just enjoyed my old pocket calculator from high school
- This is easily do-able
The rest MFTmapper does for you.
As soon as I have my new scope in hands and some time I will try out MTFmapper and report back.
-
1
-
Hi all again,
I think I have found a very usable software that we all can use to play around with MTF estimations on our own. It is far more advanced than the scripts I wrote and works really well. I encourage everybody who is interested to try it out, here the link:
It has a nice GUI and is well written. Was no problem to install on my Linux and does have a windows version, so we should be covered.
One can print out test sheets, also generate them and then place them at an adequate distance to cover the whole CMOS chip. The rest the software does for you.
Here are some examples from the homepage of MTFmapper:
Automatic edge detection and calculation of SFR (Spatial Frequency Response) / MTF charts for each edge:
Spatially resolved lens grid, as it resolves many edges over the sensor:
and lens profile as one is used from lens tests (this is contrast across the lens as a Meridional / Sagittal MTF curve
And it can do a lot more....
So I think we have our tool to use and compare
-
1
-
1
-
-
5 hours ago, vlaiv said:
Do you know what sort of differences we might expect when trying to evaluate optics MTF instead?
Good question. I posted the paper to keep in mind that we observe with CMOS sensors and they themselves have a MTF which we will have to consider as well, not only the MTF of the optics.
No, don't have a feeling yet what we might expect, but I want to try out how good we can measure the MTF in real life....
-
Regarding the Roddier test, I think it is really hard to do properly. One has to be very careful with setting up the in and out of focus images and measure the in and out focus distance very accurately to get consistent results. For me there is way more potential for errors in that procedure in comparison to shooting an edge target at distance and getting the focus right. Hmm.
@vlaiv, I look forward to see your comparison of the egde detection method with the Roddier test. Are you still aiming to do that?
-
1
-
Jupiter: Oval BA observation challenge 2022 with calculated transit times
in Observing - Planetary
Posted · Edited by alex_stars
made a challenge out of it
Hi all,
inspired by a recent post from @John
https://stargazerslounge.com/topic/383630-jupiter-the-oval-ba-and-others/
I was wondering when to observe the Oval BA. I did not find any information in drift speed and location, nor did my usual planetarium software packages (Stellarium, Sky Safari) produce any results. Thus I decided to produce some transit times myself. Here is what I did:
If you wonder how accurate the method is, you are invited to compare my calculations to your references. It should all be within minutes.
So I was thinking we could make an observation challenge out of this and whoever likes to participate could post in this thread his/her experience of trying to spot the Oval BA. Would be great if you could include information on the equipment used and the observation time.
Clear skies,
Alex
Here are the central meridian transit times for the Oval BA for January and February 2022 in UT time, the rest of the year (also for the GRS) are attached below
WinJUPOS 12.0.10 (Jupiter), C.M. transit times, 2022/01/19 14:23 Object longitude: L2 = 142.4° - 0.5990°/d * (T - 2021 Aug 16.5) Time interval: 2022 Jan 19.0 ... 2023 Jan 01.0 Output format: Date UT (C.M. of System 2) ------------------------------------------------------------------------------ 2022 Jan 19 08:34 ( 49°) 18:29 ( 49°) 2022 Jan 20 04:25 ( 49°) 14:20 ( 48°) 2022 Jan 21 00:16 ( 48°) 10:11 ( 48°) 20:07 ( 48°) 2022 Jan 22 06:02 ( 47°) 15:57 ( 47°) 2022 Jan 23 01:53 ( 47°) 11:48 ( 46°) 21:44 ( 46°) 2022 Jan 24 07:39 ( 46°) 17:35 ( 46°) 2022 Jan 25 03:30 ( 46°) 13:25 ( 45°) 23:21 ( 45°) 2022 Jan 26 09:16 ( 45°) 19:12 ( 45°) 2022 Jan 27 05:07 ( 44°) 15:03 ( 44°) 2022 Jan 28 00:58 ( 44°) 10:54 ( 44°) 20:49 ( 43°) 2022 Jan 29 06:44 ( 43°) 16:40 ( 43°) 2022 Jan 30 02:35 ( 42°) 12:31 ( 42°) 22:26 ( 42°) 2022 Jan 31 08:22 ( 42°) 18:17 ( 42°) 2022 Feb 01 04:13 ( 42°) 14:08 ( 41°) 2022 Feb 02 00:03 ( 41°) 09:59 ( 41°) 19:54 ( 40°) 2022 Feb 03 05:50 ( 40°) 15:45 ( 40°) 2022 Feb 04 01:41 ( 40°) 11:36 ( 39°) 21:32 ( 39°) 2022 Feb 05 07:27 ( 39°) 17:22 ( 38°) 2022 Feb 06 03:18 ( 38°) 13:13 ( 38°) 23:09 ( 38°) 2022 Feb 07 09:04 ( 37°) 19:00 ( 38°) 2022 Feb 08 04:55 ( 37°) 14:51 ( 37°) 2022 Feb 09 00:46 ( 37°) 10:41 ( 36°) 20:37 ( 36°) 2022 Feb 10 06:32 ( 36°) 16:28 ( 36°) 2022 Feb 11 02:23 ( 35°) 12:19 ( 35°) 22:14 ( 35°) 2022 Feb 12 08:10 ( 35°) 18:05 ( 34°) 2022 Feb 13 04:00 ( 34°) 13:56 ( 34°) 23:51 ( 33°) 2022 Feb 14 09:47 ( 34°) 19:42 ( 33°) 2022 Feb 15 05:38 ( 33°) 15:33 ( 33°) 2022 Feb 16 01:29 ( 33°) 11:24 ( 32°) 21:19 ( 32°) 2022 Feb 17 07:15 ( 32°) 17:10 ( 31°) 2022 Feb 18 03:06 ( 31°) 13:01 ( 31°) 22:57 ( 31°) 2022 Feb 19 08:52 ( 30°) 18:48 ( 31°) 2022 Feb 20 04:43 ( 30°) 14:38 ( 29°) 2022 Feb 21 00:34 ( 30°) 10:29 ( 29°) 20:25 ( 29°) 2022 Feb 22 06:20 ( 29°) 16:16 ( 29°) 2022 Feb 23 02:11 ( 28°) 12:06 ( 28°) 22:02 ( 28°) 2022 Feb 24 07:57 ( 27°) 17:53 ( 27°) 2022 Feb 25 03:48 ( 27°) 13:44 ( 27°) 23:39 ( 26°) 2022 Feb 26 09:35 ( 27°) 19:30 ( 26°) 2022 Feb 27 05:25 ( 26°) 15:21 ( 26°) 2022 Feb 28 01:16 ( 25°) 11:12 ( 25°) 21:07 ( 25°)The rest of the year is attached as text files here
GRS_CMT_2022.txt
OvalBA_CMT_2022.txt