Deadlake

4 hours ago, Flame Nebula said:

I think theoretically a scope would need to resolve to <0.1 arc seconds, but I wonder if it is the contrast that allows scopes with resolutions under 1 arc second, to sometimes show a thin dark line. 

Yes, you can find more detail here

https://telescope-optics.dish-cable.com/eye_intensity_response.htm

on a separate note if you’d re looking at planets then a 5” APO would fill a gap, none of your scope would have a MTF to match.

A C11 on planets gives a mush view compared to a APO.
Just a better light bucket for DSO…

12 minutes ago, Flame Nebula said:

Thanks deadlake. This is partly why I wonder if the C9.25 may be a 'better' flagship scope for me, as I'm sure planetary AP will be similar to the C11. But, also your post adds to my suspicion that I need a really good frac, capable of good views on doubles and planets. In theory I could mount both the sct and frac on AZEQ6 at same time, use the frac until the sct has 'caught up' with cool down, then switch to that. The az-eq6 does offer multiple options in this regard. 

I think the C9.25 and the C11 are the same faff to set up etc, maybe a little weight saved.

I have just put some insulation on the C11 to see if that helps with stopping currents forming in the tube, cloud and moisture as stopped any observations so far. 

If you are using visually I would think of another mount then the AZEQ6, I had a SXP2 which carries more weight and weighs a lot less but was such faff to setup compared with an AltZ I moved to an AZ100.

Maybe focusing on the mount might also make you observation a bit easier...

Also, C11 has a huge focal length that gives a huge image scale. Thats not a feature you will get with a refractor.

Well I'll put my 2 cent in as an owner of a C11 and various APO's. 

The last time I went out, although the sky looked like it could support the C11  the moisture content in the air was high. Meaning getting the dew heater out, a C11 should always be used with a dew shield  even in summer to keep the correct as clean as possible. 

I passed on the C11 and instead pulled out a 105 and 130 mm APO..

Again, the previous viewing night I enjoyed was away and I was in a bit of a rush to get to the club night after my daughter had drifted off to sleep.

Again I went with a 105 mm APO as that meant transporting less equipment.

Don't get me wrong when it's a good night and I'm looking at DSO's the C11 is brilliant, however other nights even when I'm not looking at DSO's or other faint objects then for multiple reasons and APO every time. The C11 is a secondary scope due to it's size... 

They do multiple

Has anyone got a AP-Z and a AZ75, any comparison at all.

How  does the AP-Z handle a 2" diagonal and a heavy EP?

I have a LZOS 105 mm @ f 6.25.

As many have stated it provides super sharp, high contrast views when the cloud allows.

Does it give up some aperture to a 130 mm version, of course however there is some thing about the sharpness and the brightness of the lens to the eye that makes you not want to give it up, I do not know why the previous owner did…

On 22/02/2024 at 16:13, Mr Spock said:

I kept it in a cool place, and despite leaving it outside for hours for extra cooling, I used to look through it and be so disappointed with the view I would not do any observing, just bring the scope straight in.

Did you ever try thermally insulating the C9.25?

I have a C11 and use it as a light bucket for low powered views. 

For high powered views I've never had a none mushy night on planets.

On 16/02/2024 at 07:03, DirkSteele said:

To live somewhere where seeing would make that worthwhile….

That and the additional 500k+ to build a climate controlled observatory so the lens is ambient and a mount the size of a small car to hold it.

Guess I can dream. 😉

You have a 185 mm finder scope, finally it would get some use! 😃

29 minutes ago, DirkSteele said:

In my old form with the sliding drawtube and 2" Feathertouch is was about 6.4kg I think which was about the same as my 2" FT 105.  I now have a 3" on the back and the weight is a little higher.  But call it 7kg, Ercole is 3kg (needs a counterweight at this weight to be super smooth so add 5kg plus bar), Gitzo Series 5 is 2.8kg and then finder and diagonal etc and mid teens kg.  Hence good to know what one considers grab and go (I think this).

Well the AZ75 is 4.5 kg and using a carbon tripod around 8 kg in total. 
The main difference is a 130 mm will work quite well on it. 
The only reason I did not take the 130 mm was the child seat in the back and I was already late. The boot was full of a dog crate.

1 hour ago, Mumia said:

If you can get it somewhere, I recommend the TMB 115. A beautiful, handy refractor. Super Feathertouch focuser, which is extendable and works with any type of bino. Dew is retractable. It may not be the lightest, but it's short. The images are delicious! Below is a comparison with Takahashi 100.

The following refractor with a certified lens, with strhel 96.8. So qualitatively, he is in the same league as his Japanese colleague.

You much does the TMB 115 weigh?

The 105 mm with a FT3545  is  around 7 kg, however compacts to 495 mm long...

I took it out to Albury cricket ground last night and although the moon was out managed to see some nebulosity around Orion, with no filter and a APM 100 mm UFF in.

Last night was also colder then expected, the Kruppax tube kept the dew away! 

To be honest it's all about how much mount can be transported, the scope choice then flows from that.

2 hours ago, JTEC said:

The 90 is a triplet, so one might expect better colour correction and, imo, it has

How long does the 90 mm take to cool down?

32 minutes ago, Alan White said:

And to think the noise made to me and @Stu over no slow motions etc.

The AZ75 is super smooth, not tried chasing a planet yet but it's almost as if the slo mo is in the pan handle as the scope glides around on the mount.

That includes the C11...

I placed a C11 on a AZ75. So far so good, the scope can be panned quite smoothly.

The Vixen carbon tripod dampens any vibration very quickly, however to give confidence of no toppling I attached a sand bag (not shown) and this made the whole structure very sure footed. 

Would it be ok in high winds, maybe with a heavier sand bag.  😀

I'll try out first and then see want else needs to be added. 

Note I use a BB chair, I can then raise and lower my seating position as needed. Another half pillar could be added as well.

How does the APZ deal with a heavy EP on the back, what happens with the balance?

15 minutes ago, Louis D said:

The 30mm is world class.  It's basically flawless.

Yep, the only competitor is the 31 mm Naglar type 5, however it's many times the price and this level of performance splitting hairs.

8 hours ago, fireballxl5 said:

Rich Field Telescope,  a scope good for wide field views at low magnification. 

Or a little more accuratly:
 

A telescope that combines the widest possible field of view with the maximum usable exit pupil.
Its magnification is just low enough for the exit pupil to be the same as the observer's maximum dark-adapted pupil size.
If the maximum pupil size is taken to be 7.5 mm, the magnification will be approximately 0.13 times the aperture in millimetres.
This is usually provided by a telescope of small focal ratio and wide-field eyepiece, and is particularly suited to observing the Milky Way, extended deep-sky objects, and comets.
A typical RFT has an aperture of 100–180 mm, a focal ratio of f/4, and a field of view of 2–5°.

Now a surprise to me is a ratio of F4, seeing as more fast refactors are in the F5-F6 range.
The rich/er part comes from the density of stars you can see/per angular resolution. 
 

22 minutes ago, DirkSteele said:

Now imagine that is Bortle 9!

That is why I wanted “portability” so it could be used under some darker skies.

like here at AstroCamp in Wales with The Sky at Night.

I was looking at this APM

https://www.apm-telescopes.net/en/apm-telescope-apo-sd-refractor-152mm-f6-with-37-zta

Dennis is going to review one on CN, at less then 11 kg and with a Strehl nulled in the green of 0.985 high expectations. 

However as ever larger is better 😀
 

Just now, F15Rules said:

My new to me SD115S (bought 5 days ago in mint condition) was bought new in March 2023 and  at that time cost £2835 including shipping.

The very latest model launched in summer 2023 is identical to mine, with the sole exception that the 3 foil spacers have been replaced with a spacer ring between the optical elements..said to eliminate any artifacts from the spacers whilst imaging.

As I am visual only this change is irrelevant to me..and my previous scope, the Tak FS128 also had foil spacers..which were totally invisible when observing.

Dave

The SD115S Mark II is £2789. 

One question I have is why choose the Vixen when the StellaLira 125 mm is around 4 kg in weight. 

I probably would have brought the Vixen as I suspect it has better optics, however I've really only got the SD103S to base my view off.

I sold my SD103S as I had a 105 mm LZOS that has better optics however does not have the lightweight freedom of the Vixen that I miss. 

I was tempted to get another one, but took a look at the SD115, the old model is £100 more then the new model, see

https://www.bresseruk.com/Astronomy/Telescopes/Vixen-SD115S-apochromatic-Refractor.html

Crazy, maybe they withhave a sale on the old model?

8 minutes ago, John said:

I probably use my 70mm less often 🙄

Luckily it didn't cost much !

Now my 105 mm is grab n’ go, why would I go smaller?

Also bino friendly as well given Y balancing.

Only 500 mm long when compressed down, no need to take off the FT.

4” at a dark site can really take advantage of the contrast.

4 minutes ago, Sunshine said:

Oh wow, you barely use it?

 @DirkSteele posted how many time is 180 mm had been used…

50 minutes ago, John said:

At least a couple of SGL members have 7 inch plus apo refractors as I recall, @stuy who has a 228mm F/9 and @DirkSteele who has a 180mm F/7. Both are APM / LZOS triplets.

There are probably others too 🙂

Roger Vine (Scopeviews) has this 175mm F/8 TMB/LZOS (I think it is his own instrument):

TMB APM LZOS 175 Review (scopeviews.co.uk)

You don't see much about the larger Astro Physics, TEC or CFF refractors on here, I agree.

@DirkSteele told me his 180 mm was around £1000 a view as it does not get out much. 😀

So from consensus around 180 mm is the larger limit in the UK?

As far as large scopes, saleries do play a big part and salaries like for like are higher in the US then the UK even taking into account health care costs. The decrease in the electorates spending power due self inflicted mortgage rate increases, for example by the popcon does not help…..

Slight topic diversion, but I do not see many APO scopes larger than a 130-140 mm aperture in the UK. 

The seeing in the UK does not support large apertures or is it the high magnification? 

There are deeper, more star rich views in a large mirrored scope, however the joy of seeing the night sky is just more when using a APO due to the sharpness of the image.

Always tempted to go up to 160-195 mm, however I feel I'd never get the use.

Back to the glass candy, here is a 130 mm LZOS triplet on a AZ100.

The AZ100 has tracking installed. and is on a TPod 110 tripod. 

For me this is a must for high power work.

First time I had a BB chair, does make all the different.

Taken in Surrey Hill, under SQM 21 skies (well they where later that night)
 

Zero sessions for me, the weather has been cloudy this January in the Surrey Hills.
 

I think maybe two clear nights, but I missed those for various reasons.

Thought this was bet place to post. Managed to purchase an AZ75 this week along with a Vixen  ASG-CB90 carbon tripod.

The result is a stable platform, AZ75 (4.5 kg) and tripod (3.5 kg) puts the total around 8.0 kg.

The tripod legs are very wide and with the spreader very stable, no chance of tipping! 

The tripod is around 50 cm's when folded, very easy to transport.

Very stable from indoor use so far and the pan handle does not bump into the tripod.



One issue I wanted to iron out is balance, I tried to just use a counter weight on the front however this would of not worked with a BV attached, in the end I deployed a YAB (Y axis balance) and now it works perfectly at all angles:

 

The brakes and tension mesh are not engaged.

This a costly purchase as I shall have to duplicate up wit the AZ!00 as well.

One question I have is why does the AZ75 feel a smoother mount then the AZ100, surely not the weight, surely an explanation somewhere?

Added some photos with the tripod folded up for transport



With out the YAB, with just a Vixen plate I think the bag would close



Compared with the AZ100 on a TPod 110