chiltonstar

This is a very useful thread which I have been following avidly as part of attempting to reboot my astro spectrometry interest! A question for the experts, in keeping with the title of the thread, are any of the commonly-available cameras able to go further into the UV and IR than the AS1224 I have, or the DSLR I normally use which runs out of steam below 420 nm or above 680 nm?

Chris

2 minutes ago, joe aguiar said:

 

i never use the 8x50 finders scopes i normally just sell them. when i use a 55mm 2" ep in the scope its almost the same power as a finder

joejaguar

....but not in a 127 Mak though, which is the OP's question.

Chris

2 hours ago, Frangipane said:

Hi sorry to resurrect an old post but I just wanted to ask how you mounted the RDF onto the finder?
I am a newbie - I just wanted to know what the stand/base is that the RDF is sitting on? I'm assuming the RDF is  a SW one , is the base thing also SW?
And can you confirm that you have used cable ties to attach the base thingy to the finderscope?

Thank you

I used cable ties (or black insulating tape which works as well) to keep the profile down a bit. I've got a twin finder bracket as John above mentions but it places the finders too far out from the scope and is a bit oversized for the relatively small scope. You can see what I mean in this image which is on my much bigger 180 Mak - it's too awkward for that even and I've dispensed with it in favour of an rdf (Rigel) on the finder as well.

Re the base: it was an old SW RDF - I partly dismantled it to leave the flat plastic bit on it which would fit against the curve of the RACI barrel. On my other Mak and using a Rigel which is far better, I've filed a spare base down a bit to make a smooth curve which fits against the barrel.

Chris

Some of the most memorable:-

- first sight of Saturn through a real telescope!

- a horizon to horizon fireball complete with sound effects (hiss-whoosh)

- M31, naked eye, huge from near the summit of Monte Rosa

Chris

11 minutes ago, johninderby said:

There is this CN thread on the GSO version of the 6”.

‘https://www.cloudynights.com/topic/647095-gso-6inch-f12-classical-cassegrain-it’s-a-winner

Looks a very pretty scope, and it's clearly you we've got to blame for the hideous weather at the mo!

Certainly a bit of coma and astigmatism in the 6" then?

Does the 33% obstruction include the baffles, or is it just based on the secondary mirror diameter?

That first light is eagerly awaited by many of us I think!

Chris

I await the forthcoming posts with interest! 

Chris

1 hour ago, johninderby said:

Coma and astigmatism don’t seem to ba any problem from the reviews I have read. It seems to be really well corrected. 

As it’s really a lunar & planetary scope spikes are a non issue but only seem to be present on very bright stars.

But aren't the deficiencies of a classical cassegrain design addressed with evolved designs like the Rumak (eg 180 Mak)? Maybe modern optical materials have improved classical cassegrains?

Chris

How significant are coma and astigmatism with the Omegon in practice - any good practical assessments from "discerning users"?

As it is a classical cassegrain design, presumably there are diffraction spikes as well?

Chris

On 07/10/2019 at 09:49, John said:

Thats good to know Chris. It must have been the earlier ones that were working at less than full aperture. Neil English was convinced that his (branded Orion USA) was nearer to 170mm and referred to it was such in his review of the scope.

Presumably Synta must be incorporating a larger primary mirror with the later models ?

 

Some have been updated including the 180 and 150 I believe - it must have been carried out some months before I got my 180 in 2015; the rear of the scope was modified as well with a 2" focuser. Some models have not been modified (eg 127 Mak), although this is such a good scope that whether it's 127mm or 119mm aperture is not that critical for most of us.

I am not sure that the Orion models (also Synta of course) were modified at the same time as those branded SW here - Skywatcher could maybe help on this point. Again, there are several threads on CN that go into the apparent and true apertures of the various Mak models made by Synta. I've taken this from another post (from Skywatcher/Synta originally) and it gives some idea of the true optical arrangement:-

Per the OP's question the SW rep listed the 180's as:
•True Aperture: 182mm
•Primary Aperture: 199mm
•Baffle Opening: 31.9mm
•Rear Cell Opening: 31mm
•Secondary Diameter: 41mm
•Obstruction by Diameter: 23%
•Obstruction by Area: 5%"

The obstruction figure quoted is for the front mirror though and does not include the baffles apparently.

Chris

2 minutes ago, John said:

Are the Skywatcher mak-cassegrains operating at full aperture these days ?

Their design used to mean that the effective aperture was a bit less than stated so the 180 was in fact a 170 etc etc.

I had a Skymax 180 for a short while but found the cool down time too long for my observing circumstances.

The 180 is a true 180 John (I've  tested mine and found 179mm when it is in focus and the rear focus position is normal (ie no long focusers to extend fl).

There are a number of threads on cool-down time and cladding on CN; my own experience is that post-cladding (insulation), cool down is not a problem for me provided the air temperature is not dropping too fast. It has not been an issue in Summer, but last Winter cool-down was slightly more noticeable on days with bright sunshine and warmish, but with clear frosty nights. To be fair, on these occasions the seeing was poor anyway.

Chris

3 hours ago, jock1958 said:

I like that RACI + Rigel finder combination as well, how does it work? special adaptor on the bottom of the Rigel to accommodate the RACI?

Nothing clever. I filed the base of the Rigel to fit the barrel of the RACI and attached it with a couple of cable ties.

Chris

7 hours ago, Paz said:

What is your insulation material and  set up, I've been thinking of insulating my Mak.

I used a roll of the stuff that B&Q sell for insulating behind radiators; Al on one side and polystyrene on the other. Makes the scope look a bit hubble'ish, but this is what it looks like:-

Chris

Interesting comment Peter. One night a few weeks back, I set up my 180 Mak, 102mm f13 frac and an ED80 side by side on an area of grass and watched Saturn for an hour to test out the hypothesis about smaller scopes sometimes giving more detail with poorer seeing. Despite the slightly better contrast in the fracs, the detail in the 180 Mak was noticeably better; Cassini was clear in all three but much finer and darker in the Mak. To be fair, I've found an improvement in performance with the 180 Mak since insulating it - it gives excellent performance now most of the time, whereas without insulation, it was some of the time.

Chris

1 hour ago, John said:

Could be very nice but will the clouds play ball

I've got a surprise clear night here currently, which is not what was forecast at all.

Ditto! Clear, but haze beginning to form as the temperature drops and dew appears. I did spot the comet though (180 Mak, x67), although I have to say it wasn't the brightest comet I've seen!

Chris

A bit more detail to show Africano better....... You should be able to fit it into your field of view John!

Chris

8 minutes ago, MimasDeathStar said:

Will that be bright enough to see in a small telescope do you think? 

John (Moderator) picked it up with his 120 ED frac, so with good conditions, it should be possible in a small scope. I've not looked at it yet, but I'll have a look this evening or tomorrow if the weather permits!

Chris

If the weather permits (touch and go here in Oxford), Comet Africano passes close to Neptune tomorrow evening (no Moon). This is a SkySafari screen shot:-

Chris

I have got it a few times now with my 180 Mak. The seeing and transparency need to be excellent though and obviously the Moon can be an issue.

With Uranus, I usually get two moons easily, three sometimes and four on a few special occasions. These distant moons are a fun challenge though but well worth a try !

My garden (where I observe from) is about SQM 20.8, slightly better when the planets are higher and further S.

Chris

I wear normal jeans with a pair of slightly-oversized cheapo M&S fleece trousers over the top. For me, the double layer works better than ski trousers which I've also tried.

Chris

Now you've seen it, next time will be a lot easier! A nice report, showing persistence pays off.

I find that with a 180 Mak, it is very much down to conditions - ie both transparency and seeing have to be good.

Chris

A slow "dance" can often be from the fact that your line of sight to Saturn from the telescope goes over something like a parked car or driveway; at this time of year with bright sunny days and colder nights, the air is a lot cooler than the ground and thermals rise causing "wave" effects. It's mainly a problem for objects near the horizon - unfortunately Saturn and Jupiter this year have been near the horizon! If you can move the scope to something like grass it may be better.

Chris

11 hours ago, John said:

I got Triton list night with my 12 inch dob. Using high powers seems to help - I was at 450x. Triton was clear with direct vision last night. I have seen it with my 130mm refractor as well.

Triton was pretty obvious to me as well this evening, even with my smaller scope; very good transparency though and the Moon has moved round a bit. . The view was best at x350 with my scope/eye. With moonlight shining directly on the scope, I had to use my black hood, and then Triton popped in to view (DV) easily. Interesting to see the amount of movement of Neptune cpd with the star.

Chris

47 minutes ago, johnturley said:

I've never been able to see Triton visually even through my 14 in Newtonian.

John 

I've caught it a few times with the 180 Mak, but the conditions have to be excellent (seeing and transparency) to catch a mag 13.6 object with a relatively limited aperture. 

Chris

I had a look this evening with the 180 Mak. Uranus was visible in the finder even with the Moon close by, and a clear light blue/green disc at x270 through the scope, although the seeing was only average. Only two moons visible - hardly surprising really with such a bright Moon/haze background.

Neptune was barely visible in the finder, although a nice blue ball through the scope. I couldn't make out Triton tonight against the very bright background, again hardly surprising.

A nice challenge though with such bright moonlight and a hazy sky!

Chris

On 03/09/2019 at 21:11, niallk said:

Nice one!

I've had some memorable views of a sharp greenish disc on Uranus with 4 maybe 5 moons in averted vision, plus Neptune and Triton on a run of nights with good seeing in my 15".  Looking fwd to trying again this year.

Might not be the visual treat that Jupiter or Saturn is, but there something about seeing them with your very own eyes... quite special imho.  We know so little about them really.

Very true - I find there is something very special about them, to me they look like little three dimensional coloured balls scudding along across the Fov. 

Chris