Goodbye dobs & farewell

[Peter Drew]

It depends on whether the telescope is housed or not. It takes me less than 3 minutes to set up a 30". If the seeing is so poor only a 4" will perform I do something else. 

[John]

On cool down times:

On deep sky I find I can use my 12" dob virtually straight out of the house. If I want to view the Moon, planets or double stars at 100x plus then the tube takes 30-40 minutes to cool to a point where I can get the best from it.

My Vixen 4" frac takes 30+ minutes to give optimum high power views. My 4" Tak has virtually no cool down time (thinner lenses at F/9 plus a 95mm tube ?). My ED120 takes 20mins+ to properly cool and my 5.1" triplet frac needs around 40 mins.

The Tak is therefore the nearest to a complete "grab and go" scope that I have. The Vixen has always surprised me with how much cool down time it needs. I've assumed that at F/6.5 the glass in the lenses is proportionally thicker and it's tube is quite a bit fatter (112mm) than the Tak. Once cooled the high power images are very good but a little patience is needed. The 12" dob cool down (no fan used) is more or less what I'd expect although I've been pleasantly surprised by it's low power views when still relatively "warm". The 5.1" triplet is around what I expected, cool down time wise but, oh my, the views are worth the wait

I really ought to downsize from 5 scopes given the amount of sky-time both they and I get in the UK but I really can't pick one that I would not almost immediately miss

[Pig]

I have to say the best views I have seen are through the DOB's at the SWSP earlier in the year.... they must be really hard to better. However, I do love the 110mm refractor, its widefield views and wonderful ability to deliver colourful and pinpoint stars. .... The 8" SCT also has its place as it is nothing short of fantastic for planetary and lunar.

Portability is key though and with my current kit I can be out observing within a very small time frame

[mikeDnight]

2 hours ago, Peter Drew said:

It depends on whether the telescope is housed or not. It takes me less than 3 minutes to set up a 30". If the seeing is so poor only a 4" will perform I do something else. 

Now Peter, you know that deep down you really love that fabulous 4" Vixen fluorite you've been caught hiding behind from time to time. ? And I'm sure you'll never forget the night back in 2003 when an elderly visitor to the Astronomy Centre asked the question "Why is Saturn so much better in this telescope (the Vixen fluorite) than in anything else?" And again in that same year, on an evening when around 300 visitors turned up to look at Mars. I'd purposefully set my FS128 up in the corner of the field far from the crowds. All was going well until late in the night, a lone wanderer stumbled upon this antisocial astronomer hiding in the darkness. The gentleman politely asked if he could take a look through my scope. My heart sank slightly when I realized I'd been found out, but it almost stopped beating when the visitor shouted out in the darkness to his friend across the field ? "Abdul, come and take a look through this one, its the best one here!" I cringed ? as a stampede of visitors rapidly surrounded my scope and my personal session was abruptly brought to an end for that evening. ? 

Now of all the big scopes of a'll kinds in use that evening, I personally believe that the FS128 was not the best performer. To my mind, the best scope was the 8.5" refractor, but it was still a refractor. ?

Mike

It's no use trying to hide, we can still see you! ?

[Stu]

Lovely looking Vixen Mike, is that an f9?

[Peter Drew]

Well that's blown my cover!  . Yes Stu, it's F9 (slightly shortened tube for binoviewer use without a Barlow)

[Davesellars]

17 hours ago, John said:

Thats an interesting comment Dave. I find my ED120 shows very, very little CA at focus. Nothing around the limb of the moon and only very slight CA around the brightest stars. Having had the chance to compare the ED120 with my Tak flourite doublet and Lzos triplet (both of which show no CA at all) I've realised just how good the ED120 objective is. I've owned ED80's and and ED100 and the ED120 seems to be in very much the same league CA-wise.

To be honest John, I only noticed the CA when I was doing astro photography with the 120ED.  There is a difference between the 80ED and 120ED. While perhaps not perceptible by eye (like yourself I could not see CA visually) would it make a difference to the sharpness of image etc visually especially when applying equally high powers?

[Stu]

30 minutes ago, Peter Drew said:

Well that's blown my cover!  . Yes Stu, it's F9 (slightly shortened tube for binoviewer use without a Barlow)

Ah yes, thought it looked a little stubby .

I might just have one of these coming my way very soon which is exciting!

[John]

59 minutes ago, Davesellars said:

To be honest John, I only noticed the CA when I was doing astro photography with the 120ED.  There is a difference between the 80ED and 120ED. While perhaps not perceptible by eye (like yourself I could not see CA visually) would it make a difference to the sharpness of image etc visually especially when applying equally high powers?

The ED120 seems as sharp as anything to my eyes. I use 257x and 300x with it quite regularly. Imaging might well reveal the differences although with the ED120 I believe Synta went that extra mile to get the figuring just right before releasing the model. Maybe this attention offsets the normal differences that one might expect to see between an 80mm and a 120mm ED doublet @ F/7.5 ?

@Stu: I'll be very interested to hear your views on the Vixen 102FL when you get it. They seem to occupy an almost legendary status

 

[Stu]

2 hours ago, John said:

The ED120 seems as sharp as anything to my eyes. I use 257x and 300x with it quite regularly. Imaging might well reveal the differences although with the ED120 I believe Synta went that extra mile to get the figuring just right before releasing the model. Maybe this attention offsets the normal differences that one might expect to see between an 80mm and a 120mm ED doublet @ F/7.5 ?

@Stu: I'll be very interested to hear your views on the Vixen 102FL when you get it. They seem to occupy an almost legendary status

 

I'm looking forward to it too John. I'm hoping it will be in similar territory to the FC100DL but we will see.

[John]

19 minutes ago, Stu said:

I'm looking forward to it too John. I'm hoping it will be in similar territory to the FC100DL but we will see.

It should compare excellently I'd have thought - probably close to identically. I believe the obective of the Vixen 102FL was made by Canon-Optron who were also responsible for the Taks. Same objective design as well - Steinheil.

 

[mikeDnight]

1 hour ago, John said:

It should compare excellently I'd have thought - probably close to identically. I believe the obective of the Vixen 102FL was made by Canon-Optron who were also responsible for the Taks. Same objective design as well - Steinheil.

 

From what I've read some time back on CN, the Vixen FL102 rear fluorite element remained uncoated. At the time that the FL102 and the original Takahashi FC100 refractors were in production, the coating of fluorite lenses had not been mastered. I remember Tak making a big thing about the FS series having Hard multicoatings on their front fluorite elements. The new FC user manual comments briefly about the hard multicoating of fluorite, implying that the new FC fluorite element is also hard multicoated. I couldn't say why, but in side by side comparison between Peters FL102 and my own FC100DC, both scopes were terrific optically but the FC had a vibrancy about it that wasn't evident in the FL. I wasn't the one that pointed it out, it was two other observers that commented about the difference, though it was noticeable. May be the coatings made that difference or possibly the new eco glass mating element. It would be good to have the DL alongside the FL for a careful comparative session.

Mike

 

[timwetherell]

On 11/12/2016 at 10:12, Peter Drew said:

It depends on whether the telescope is housed or not. 

Yes indeed! Not everyone's fortunate enough to be able to have an observatory, if you are it's a total game changer. One should never underestimate the importance of convenience in amateur astronomy - which I guess is the entire point of this thread