Posts Made By: Mark Holden

john welch said:

Here's an old question. Just hopin' for new answers. 8)

I have an older 9mm Nag that needs an eye cup, plus a few other various ones needing the same).

Any thoughts?

Thanks,
John

My understanding is Televue has or can get eyecups for any of their eyepieces including ones that are out of production.

I've had good luck ordering replacements for the Meade Series 4000 14mm and 8.8mm UWA from Agena



I was impressed enough with their service that I'll check with them before ordering anything they're likely to sell.

George Kiger said:

Is it just me, or do others find it odd that a number of 155 owners are selling because they are getting a 160. I do not own an AP scope, and probably never will (a $ issue), but why would someone do this? Not challenging the action, just curious.

Because they can?

The 160 gathers a whopping 6.5% more light.

But it's an F7.5 instead of F7. So the focal length is 10.5% longer. That alone might be a good enough reason for a person who enjoys viewing planets.

I don't know how the two compare optically, but I think the 160 is the first air spaced design for AP.

Some folks might have the 2.7" focuser on their 155's and want the 4".

And some folks just probably want to own one of each.

The RC scope have a larger central obstruction than other types of scopes - and this reduces contrast, and makes it a little tougher to get your eye in the right spot.

Cyril Mundell said:

I am puzzled at why someone using an AP is using a budget eyepiece? Also, rather than one budget eyepiece compared to another, it would also have been of interest to see the Burgess compared to a TeleVue 4 mm Nagler or something in its class.

The 4mm Burgess/TMB planetary eyepiece has less light scatter than a 3.5mm Nagler - but the Nagler has a wider field of view.

But one reason for using this eyepiece is the eye relief and large eye lens makes it an easy eyepiece for members of the public to observe with at a star party.

Steven Keaton said:

How do I even ask this question?

Background: I have a magnificent TEC 6. This is a great all around scope. Lightweight, enough Aperture, great build quality, and cosmetically, looks awesome on my GM-8.
Downside is cooldown, and possibly 6" is a bit much to reach ambient temperature quickly in Northern, KY. Coupled with an almost constant haze. I believe these are factors that take away from performance that this scope is capable of...

I have been thinking a lot lately about an FS102 that I had which performed marvelously regardless of seeing conditions. It seemed to cut through any reasonable amount of haze. Cooldown was never more that a half hour.

However, I would like more than 4".

To add to my dilema, I had a Tak FS128 for about 6 months. It was a beautiful performer, but it seemed to be hindered by haze and heavy light pollution that I am subjected to in my area.

Question: What APO might fit my needs? Something in the 4.5" range? The TMB115 Lightweight seems attractive. Perhaps the very similar SV115 or even a Vixen.

I am strictly a visual observer. No CCD imaging in the forseeable future.

Any opinions on a very familiar question?

Steve

I have a TMB 115 CNC, and love the scope. It cools down quickly. It is just barely airline carry on portable.

The SV115 is the same objective, with a different tube.

Either should give beautiful high contrast images.

In a slightly larger size, you might consider the 130 f9.25. It won't be quite as portable, but you might prefer the slightly higher F ratio.

A lower cost alternative is the Orion 100mm f9 apo. A 14 year old member of my astronomical society just got one, and considering how inexpensive it is, it's nice. We have noticed it seems to dew up quicker than our TMB's though.

Good luck.

Regards,

Mark

Berry Nellums said:

..... I am trying to establish an extended image plane fot my TAL 2000-K Maksutov to use with my binoviewer. The TAL
does not allow enough in travel to do so. I placed a 2x
barlow in my setup and I got the image plane extended enough to use the binoviewer,but the image quality was not
good (probably because my barlow is of low quality) I guess
now for my question to the forum would be to try to find out
if someone knows if a less than 2x barlow is made and by whom. I don't really need that much extension in my system to use the binoviewer and certainly did not like my matching 20-mm eyepieces being changed into a 10-mm setup.

Thanks
Berry

TMB makes an incredibly nice 1.8 barlow, but it'll make your lack of infocus worse.

Edward J. Portka said:

I have a 4"APO refractor with a F/L of 900mm and F/ratio of 8.8. What are my best choices for three eyepieces of low, medium and high power. I wear glasses (not always) and have some astigmatism(not bad). Price should not enter in the choices you recommend. I have a quality scope and it needs quality eyepieces. My focus is on luner and planets. Your recommendations will be very much appreciated. Thank you!

Hi

I'd like the 14mm UWA (Series 4000 if you can find one) for medium power.

On a shorter eyepiece, I'd go for a TMB supermonocentric. These have a narrow field of view, but incredible contrast for planets. The problem will be eye relief - they don't have much. They're available in a variety of focal lengths - I'd go for something in the general range of a 5. If you can, it would be great to borrow one from a friend first.

An alternative for high power is the Burgess/tmb planetary eyepieces, but there is a reflection problem in current production - it can be fixed with some Krylon flat black spray paint - or you can wait a while for Bill to get them fixed. (Bill isn't known for fast fixes) The first night with decent seeing where I could try mine, it wasn't an issue because I was observing through thin fog. But on a clear night, it was annoying. This eyepiece has a wider field of view than the super monocentrics, and plenty of eye relief.

I'd also suggest a TMB 1.8 barlow. It's the nicest barlow I've ever used. I also like the 2x clave barlow.

On low power, you might look at a 41 Panoptic or a 31 Nagler. Both will give a nice wide field of view.

Mark Trotter said:

I know everyone asks a question like that but I'm a beginner and this is the first time I have posted. I was looking for a telescope that I can put in my car but wouldn't weigh so much i couldnt assemble is somewhere else. I know from reading other forums that people don't like to reduce the size and inturn reduce the power. I'm just looking for something I can see deep space objects nicely. Sorry again for the same type of post but I'm just wondering what you guys think.
-Mark

I'll second Jims' suggestion to visit your local astronomical society and spend some time looking through other folks scopes, and talking to their owners to get a better handle on what kind of scope you'll like.

Some folks love Dobsonians and feel they give the most bang for the buck. Others feel the mount is awkward to work with and don't want anything that's not on an equatorial mount.

SCT's look nice and compact, but by the time you include the tripod they're not much easier to transport than a Dob, and will take longer to set up. They also take longer to cool down for use, the correctors are prone to dewing up quickly, and they have a narrower field of view - though this makes them pretty good for planets.

No matter what kind of scope you look at, odds are some folks will love them, and others will feel they're a poor choice.

The important thing is to find a scope that meets your goals - and if you're a beginner, you may not even know much about what your priorities will be.

Scopes I encourage you to evaluate include -

Dobsonians
Newtonians (a dob tube on an EQ mount)
SCTs/maks
Refractors (apo and achromats)

Take your time - a little extra effort spent researching your options will pay off in the long run.

Mike Damato said:

Hi all,

I've been perusing this forum and whatever other ATM information sources I can find on the web, and it seems that there is some disagreement about the effect of tube material on cooldown issues.

Some people seem to think that an insulating tube material is best (sonotube, fiberglass, etc.) whereas others favor a high thermal conductivity material such as aluminum. In my case I'm leaning towards aluminum because of weight issues anyway, but it seems to me intuitively that initial cooldown will be faster, and ongoing thermal effects throughout an observing session less disruptive, with a material that conducts heat readily.

Is this an old controversy that has already been settled? Can anyone point me to an article or something that definitively settles it? I'm inclined to think that the more thermal conductivity the merrier, and in fact I'm thinking of using an aluminum tube and leaving the outer surface unpainted altogether. I can't get away from flocking the interior - aluminum is awfully shiny! - but finishing the outside seems unnecessary.

Am I all wet here?

Thanks,

Mike

Hi

Phenolic tubes used for high power rocketry are supposed to be quite good.

Here's a link to a web site for this kind of tube.



Apparently, an advantage this type of tube has over aluminum is less thermal expansion.

Luke Leege said:

I sent back my 10"RCX due to too many problems. So with my limited $$, what do I buy? I'm thinking G-11 or CGE and a TaK 102??? I don't want to deal with forks anymore and I primarily want to image with my 20D. What do you recommend, Roland? The refund is burning a hole in my pocket.

One thing to consider is some scopes will need a flatener, and others can get by without one.

When I bought my TMB 115, I checked with Thomas Back, and the information I got from him boiled down to I probably don't need a flatener for use with a D70. Your camera has the same size chip.

I don't have the specifics handy, but it worked out where the very tips of the corners wouldn't be very good, a few percent would be "good", and about 90% of the frame would be excellent.

If you decide to go with a TMB objective, you could call him to get the specifics for the scope you're interested in.

Money that doesn't need to go into a flatener could go into a slightly larger objective.

My guess is if you're friendly and patient, almost any of the better scope makers would be able to get you similar information.

I use my scope on a GM8 with a G11 tripod. It's fine for photographic use, but you do need to guide for long exposures.
On the other hand, I am likely to upgrade to the new small AP mount when it becomes available, as the AP mounts are a step or two above in build quality, and seem to track better.

Good luck with whatever you decide.