John

The Aero ED eyepieces are pretty decent 2 inch eyepieces. They can be bought for around £50-£60 apiece on the used market. They are better corrected than the lower cost 2 inch eyepieces and also reasonably light for 2 inchers. They have a 70 degree apparent field of view and come in focal lengths of 30mm, 35mm and 40mm.

The range of focal ratios of your scopes (F/4.7 to F/7) is reasonbly wide. The F/4.7 will pose the greatest challenge for an eyepiece in terms of remaining sharp across the field of view so you may need to accept some compromise there unless you are prepared to spend big bucks or stay with a smaller apparent field.

Thanks for the heads up about this event

Simulating this in Stellarium makes it look rather unspectacular - penumbral eclipses cause more of a slight darkening of the surface than the "blood red" effect don't they ?

Here is a link to something similar to the process that Steve / Woodblock describes:

http://www.stark-labs.com/craig/llcc/llcc.html

14 minutes ago, woodblock said:

I'm fairly new to this myself but I found that my laser collimator had to be collimated itself before I could use it to collimate the telescope.  On the laser there were 3 tiny rubber caps around the circumference. Take the rubber cap off and there was a tiny screw adjustment underneath. The way I did it was to make a cradle for the collimator so that I could rotate it while it shone on a wall. Then rotate the laser and adjust the screws so that the laser spot didn't move. It's a bit fiddly but not too difficult.

Steve

 

Steve - I've split Adams questions regarding collimation off into a new thread here:

I've copied a link to your comments into that new thread because I messed up the splitting process a bit

Hope thats OK.

One glass of wine too many for supper I fear

I made a bit of a mess of splitting this off into a new topic for you Adam

Anyway, here is what @woodblock posted in your other thread:

Sounds like you need to collimate your laser collimator as Steve says above. I'll split this thread so you get a new one on this topic otherwise the change of topic might get overlooked.

You don't actually need a moon filter to observe the moon. Some folks find that they like to use one and some folks don't. It's not mandatory.

Do throw the sun filter away if you find it - they are very dangerous.

Otherwise, hope you enjoy the scope !

Great report Garry

You have a set of fabulous scopes there !

I wonder how the AZ Pro mount would handle my LZOS/TMB 130 F/9.2 triplet

Is your AZ Pro stock specification ?

13 minutes ago, omo said:

....I did have it out a couple of nights ago, then my neighbour went out and put on his security light 😡....

If you get in touch with Rowan Astronomy they will send Hypno-Disk round to sort your neighbour out

Even if the scope is a bit out of collimation the moon should focus quite sharply. Accurate collimation gets you the last 10-15% of performance that the scope can give but even with some collimation error the scope should provide reasonably nice images of the night sky targets.

Which eyepiece did you have in the scope when you could not get the moon into focus ?

If you have eyepieces and a barlow lens with the scope, dont use the barlow lens for now and just try using the eyepiece with the longest focal length (ie: the highest number in mm).

Actually collimation adjustment facilities for the objective are included in some of the less expensive achromats from Skywatcher and Meade.

With triplets, as well as the tilt of the lens, the centering of the optical axis of the elements relativel to each other is critical. Triplet collimation is best left to experts for this reason.

The Tal APOLAR 125 had 6 lens elements arranged in 3 groups along the length of the tube. I'd really not want to try and collimate one of those !

Do you think that these will replace the Evostar ED DS Pro range in due course ?

I notice that the OP's dob is a Revelation 8 inch. I thought those had lazy susan type roller bearings to the azimuth axis fitted as a stock item ?

9 minutes ago, jaydee3839 said:

John, how do I figure exactly (or approximately) how much eye relief any given barlow (such as Baader Classic Q 2.25x), adds to an eyepiece?

Its difficult because it depends on the focal length of the barlow lens optics (they do have a focal length like eyepieces do) and this spec is not widely available.

Short format barlow lenses increase the eye relief more than the longer ones. I believe it can be as much as a 50% increase.

Unsing a barlow lens with a long focal length eyepiece does not always give satisfactory results. This is mainly because the eye relief (distance that the eye needs to be from the top lens of the eyepiece) is already long with such an eyepiece and a barlow lens increases that futher. So you get the image amplification but the eye relief increase may well mean that you need to "hover" your eye someway off the top of the eyepiece which is neither relaxing or comfortable.

@mikeDnight makes an interesting alternative proposal above.

My 12 inch dob has smooth tracking on both axis. Just teflon pads but in the right places and running against a suitable laminate surface. No problem tracking at 300x or more (as I have been tonight).

Getting the axis to move smoothly is the key and well worth the effort.

Just a quick point about the Baader 2.25x barlow. When you unscrew the lens element from it and screw that into the barrel of a 1.25 inch eyepiece the barlow does indeed give a 1.3x (approx) amplification. To do this you need eyepieces that do not have any optical elements or other obstructions within the 1.25 inch barrel because the optical elements of the barlow need about 15mm clearance up inside the barrel. A number of the eyepieces you have listed have optical elements within their barrels which will prevent the Baader Q-Turret 2.25x being used in that way.

On the magnification spread you have, it seems crowded to me in the sub-100x area and lacking in the medium to higher ranges (eg: 100x - 250x).

Have you got a "dob knob" fitted to your scope ?. It helps with moving the scope smoothly.

Phase of Venus looking nicely defined tonight at 227x with my 12 inch dob. A UHC filter takes some of the glare away and crispens the view up a bit.

I think the angle of illumination of these very fine lunar features is important to detecting them. Its possible that with some, that the "window of opportunity" is very short - even an hour either side of the optimum time might make all the difference.

A further review of one of these interesting scopes has appeared recently on another forum:

https://www.cloudynights.com/topic/686955-gso-8-inch-true-cassegrain/

The most interesting comments in that review for me, relate to the effective aperture of the instrument. Are there variations in spec for these scopes ?

6 minutes ago, Stu said:

What's interesting is that I've seen the Alpine Rille in my 4" Tak a couple of times, but I think I've only managed 4 Plato craterlets with it. I guess the fact that the Rille is a long feature makes it easier, somewhat like the Cassini Division? Illumination has to be optimum otherwise it's not possible.

That is interesting. I've yet to see the Alpine Rille with any scope other than my 12 inch dob but that might just be a case of things not quite falling into place when I've been trying with one of the refractors.

I also think these targets that are pushing the envelope in performance terms place high demands on the last links in the observing chain, ie: the eye and the brain. We don't talk about those observing tools that much but they are crucial of course.

Seeing conditions are the master here but when they are good I've been able to see sections of the central rille that runs down the lunar alpine valley with my 12 inch dob at around 300x. The rille is 1000 metres across at it's widest which would equate to a resolution of around .6 of an arc second.

That is the finest detail that I've been aware of resolving on the moon so far. On really good nights I've also managed to see 11 craterlets in Plato the smallest of which are just under 1km I believe.

The illumination situation of the features being observed plays a big part in their visibility - shadow really does help in picking up a piece of terrain.

3 hours ago, Carbon Brush said:

......This early high risk time is followed by a long period of reliable operation, with few failures. Often many years....

......Then after many years, a number of factors come together to cause an increasing failure rate.....

......What about other parts of the equipment? They degrade with age......

 

This refers to astronomers, surely ?

I'm definitely NOT worth 60% of my original price, thats for sure

1 hour ago, Stu said:

The feel of the worms has improved alot John so I think the slow motion cables work well now. It was a matter of turning the worm gear adjustment and also the type of grease used in them.

Yes, I fitted the new worm units supplied by Rowan which I understand had a different type of grease in them. Rowan have been really responsive during the beta testing of the AZ 100. Such a refreshing approach to launching a new product