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Helios 8" Newtonian telescope OTA. Equivalent with Skywatcher Explorer 200P.
Has some cosmetic markings, but otherwise in excellent condition.
- 1.25" and 2" eyepiece adapters
- 9x50 finderscope
- long Vixen style dovetail
Price: £130 (negotiable)
Celestron Astromaster Kit is available for £20 extra
Mount not included.
Pick up only in Oxford.
By Anthony RS
Is anyone here using the TS Photon 6" F4 newtonian? I'm about to purchase it but I have some doubts and questions:
1- Does it hold collimation well, at least in a single session?
2- Is it impossible to balance in DEC due to its small dovetail or is it possible but harder?
3- Is the focuser rigid enough or does it introduce tilt?
4- Will collimating it be a nightmare?
5- I'm really picky when it comes to coma, should I expect some coma on edges even while using the Skywatcher Aplanatic F4 CC?
6- All in all, do you advice me to buy it or have some other option in the same price range.
By Michele Scotti
Hi everybody - I'm humbled that some of you are following the thread on the 800mm telescope. I thought it was worth starting a sub-topic specifically related to the mirror making.
So as the works on the mount got halted by the lockdown we had some time to virtually meet-up and discuss the optics for this project.
The onset was pretty straightforward with an 'if we are doing this we are making the mirror'. And that sorts out the make vs buy, I suppose.
As of now, the only two things decided so far are the diameter -at 800mm- and the f/3.3 - of course we can accommodate some variance.
Some aspects of the making are pretty unchartered territories for our club so I'd like to seek some good advice from anybody in terms of direct experience or rather point us at some resources/threads.
Back-ground: to make it short, our senior member had three 500mm f/5 done years ago. He did of course faster optics up to f/3 among many other mirrors - I actually never asked him how many, uh! He has always worked with full tool and has no experience with slumped glass. Btw we do have some experience in slumping glass but -weirdly enough- not in machining.
During our initial discussions we boiled the scenarios down to 3:
float glass, 35/40mm thickness considering 15mm of sagitta. This is a thermal challenge with its big outward mass, it's going to make the machining more of a challenge and the stabilization time longer float glass, 25mm (which seems more of a commercially available), slumped. Trading the thermal challenge with the slumping borosilicate, 25mm, slumped. Tbh this is just a better version of the previous point at a cost that is not prohibitive
What are the sources of glass in Europe for thickness over the bog standard 25mm?
Disclaimer: this is surely an ambitious endeavor and by no means we are underestimating that. Not only the bigger diameter is a step-up; the fast optics is a challenge too.
To start with we have some questions about slumped glass. It looks like an attractive, modern approach to mirrors that exceed a given diameter. I think I saw already some threads specifically about the slumping itself - that's golden.
However it's the grinding/finishing/parabolizing that is puzzling us. Are there specific techniques or is it the same as the flat back glass?
Also, how do you support the mirror? Would a support that replicates the telescope mirror cage be appropriate - a 27-point in our case? Or is it a matter to build a concave support that holds the back of the mirror? How accurate/solid should that support be?
Any experience out there??
I reckon that's enough as a start - thanks everybody in advance for your contribution.
Stay safe! Michele
Hi guys, firstly - sorry if this is posted in the wrong place.
I've just ordered a Canon 600D to start doing some astrophotography and it arrives tomorrow - I'm stoked. I've been wanting to get into astrophotography for a while now and I'm so happy to finally be pulling the trigger.
The last item on my shopping list is a solid beginner telescope which would couple well with my Canon 600D. The research I've done is all pointing towards a newtonian reflector.
My primary goal here is to take some pictures of stars and planets with the Canon 600D attached to the telescope. I've been looking at the Sky-Watcher 114/900 as it's relatively cheap, which I think is great for someone just starting off - but was wondering what your opinions were seeing as you've all been through this before. Do you have any other recommendations? I'd like to keep my budget up to £300, and that's stretching it really.
Thanks for taking the time to help!
Scope: 20” f3.6 Lukehurst Dob with Paracorr (fl = 2089mm & f4.1).
Night Vision: PVS-14 with Photonis 4g INTENS.
Eyepiece: Plossl 55mm (f2 x38).
In spring 2019 I created a Sky Safari observing list of 214 highest brightness galaxies in the night sky above.
I have observed 134 of the 214 (the others have not been well placed over my garden when I have been outside).
In my first pass through these 134 galaxies, they were graded 0-3 (where 3 means "clear spiral arms" and 0 means "nothing to see here!")
I have now completed a second pass through the grade 2 and grade 3 galaxies. This has resulted in some movement between bands based on my now greater experience and having a better idea of what I expect to see.
My latest graded lists contain 38 grade 3 galaxies and 30 grade 2 galaxies (when combined this gives a list of the best galaxies to view when using military night vision technology combined with a low power eyepiece (using the TeleVue PVS-14 adapter).
[Note that lower power eyepieces give the best spiral arm results as they “increase the effective focal ratio” of the telescope/night vision system which really helps increase the detail seen at the eyepiece.]
As we are still in galaxy season 2020, now seemed a good time to re-publish my findings so others have the opportunity to observe some of these fantastic galaxies before they become “unavailable” for another 10 months…
Grade 3 galaxies (the best of the best).
M51 M61 M64 M65 M66 M81 M90 M91 M94 M95 M96 M99 M100 M101 M106 M109 NGC891 NGC2403 NGC2903 NGC3184 NGC3628 NGC3631 NGC3726 NGC3893 NGC3953 NGC4051 NGC4216 NGC4274 NGC4449 NGC4559 NGC4565 NGC4618 NGC4725 NGC5248 NGC5371 NGC5746 NGC5907 NGC6946
Grade 2 galaxies (good but the arms are not quite there…)
M82 M88 M98 M104 NGC2537 NGC2768 NGC3294 NGC3344 NGC3373 NGC3596 NGC3646 NGC3675 NGC3718 NGC3729 NGC3813 NGC3938 NGC4013 NGC4214 NGC4293 NGC4389 NGC4490 NGC4517 NGC4535 NGC4625 NGC4762 NGC5005 NGC5364 NGC5383 NGC5775 NGC6015 Hopefully someone will find this useful information, next time they plan a galaxy observing session...
Note that my dobsonian uses an Astrodevices Nexus unit which I control using Sky Safari. Here are my exported observing lists (which you can import into your Sky Safari app should you wish to do so?)
Grade 3 Galaxies.skylist
Grade 2 Galaxies.skylist
1. email them to your phone/ipad,
2. read the email on your mobile device and after clicking on the attachment, you should be offered the chance to “send to Sky Safari” by your email app…
3.Sky Safari will open and give a message “Observing List Created”.