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Equipment Discussions >> Reflectors

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Muffin
member


Reged: 09/27/13

Loc: Pinelands-near Cape Town,South...
Zhumell TYCHO 254 new
      #6104003 - 09/27/13 11:42 AM

Good afternoon - Im not really new to CLOUDY NIGHTS - it just refused to accept the name and password I had used some time ago so I had to re-register. Anyway I recently acquired a Zhumell TYCHO 254 which is basically a 10 inch f/4.7 newtonian equipped with a barlow lens between the primary and secondary mirror and giving effectivey a 10 inch f/6.3. I am the third owner-I believe it was made sometime around 2008 - the manual available on the web is very incomplete as regards the optical configuration and doesnt even mention collimation. I have tried contacting Zhumell but so far no luck - the email address in the so called manual may be incorrect and Zhumell was based in Proctor,MN, USA. Their web site no longer mentions the telescope nor does it give a contact email so now I have to rsort to other means. The basic problem with all three owners is the very objectionable coma - its advertised as being able to take up to 600x but even at 50x the coma renders it almost useless. What Iam trying to do is find anybody who knows the slightest bit about the telescope - I saw one review in which the telescope was given a score of 4 out of 5 so maybe some telescopes were okay. The coma does not disappear irrespective of the collimation or how changed- the "tail" maintains the same position over the entire field - changing primary or secondary mirror collimation makes absolutely no difference. I am now beginning to suspect that the barlow lens - an air-spaced achromatic doublet is installed "back to front"- its the only variable left that has not been changed. I am no stranger to telescopes etc- was a professional astronomer before I retired for over 30 years and regularly used telescopes considerably larger than 10 inch aperture. In my pre-professional days I made about a dozen reflectors - up to 12 inch aperture so again Im no stranger to this aspect BUT the Zhumell has me currently beaten. Its a well made scope so I cant believe that the telescope as originally sold was a "dud". I see Zhumell no longer make the 10 inch euqatorial model with the deluxe version of the Vixen EQ5- I believe its now known as the Grand Polaris DX model - complete with drives on both RA and Dec axis and it has been replaced by a 10-inch Dobsonian. Can ANYBODY help?
I was employed at the Republic Observatory -Johannesburg for 5 years where I managed the International Planetary Patrol Program for Lowell Observatory at the observatory for a period of 5 years using a 26.5 inch refractor working at f/90. At the completion of the program I transferred to the S.A.Astronomical Observatory where I worked in Parallax and Astrometry for about 15 years, before then moving to infra-red photometry, followed by some CCD photometry and finally photometry in UBVRI. I retired in 1999 and now spend my time tracking artificial satellites using video and a large format FLI8300M ccd camera- also have the two early Meade DSI cameras. Although Im now called "muffin" my correct name is Greg.


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Shneor
scholastic sledgehammer
*****

Reged: 03/01/05

Loc: Northern California
Re: Zhumell TYCHO 254 new [Re: Muffin]
      #6104437 - 09/27/13 03:21 PM

If it truly is coma that you are seeing, you might try a coma corrector. But if collimation makes no difference, it's hard to believe that the distortion you are seeing is classic come. The only possibilities that come to mind are that the barlow lens is not orthogonal to the plane of the focal path between the primary and secondary, or is not centered (or is just defective).

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Muffin
member


Reged: 09/27/13

Loc: Pinelands-near Cape Town,South...
Re: Zhumell TYCHO 254 new [Re: Shneor]
      #6104648 - 09/27/13 05:38 PM Attachment (34 downloads)

Many thanks for your reply Shneor. I call it coma for want of a better name - could well be something else as it does not behave like the "classic coma" - at the moment I am just plan beat.

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Muffin
member


Reged: 09/27/13

Loc: Pinelands-near Cape Town,South...
Re: Zhumell TYCHO 254 new [Re: Muffin]
      #6104660 - 09/27/13 05:48 PM Attachment (33 downloads)

Ive attached the best Ive been able to achive so far - its the full field of view ( 48 x 32 arc minutes) and done with a Nikon D3100 at prime newtonian focus - 30 seconds duration. The bright star is Alpha Centauri.Under some image magnification one can see the comet tails are all the same across the entiure field of view. Ill also attach a picture of the secondary holder and the complete telescope.

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Muffin
member


Reged: 09/27/13

Loc: Pinelands-near Cape Town,South...
Re: Zhumell TYCHO 254 new [Re: Muffin]
      #6104670 - 09/27/13 05:54 PM Attachment (31 downloads)

The picture just posted shows the secondary and the barlow lens attachment - very well made. The "hole" in the side is where the light from the secondary exits to eyepiece holder-you can see part of the secondary mirror and above it the barlow attachment - about 2 inches in diamater and this faces the primary mirror. Will now do final posting- the Zhumell scope in my backyard.

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BigC
Carpal Tunnel
*****

Reged: 09/29/10

Loc: SE Indiana
Re: Zhumell TYCHO 254 new [Re: Muffin]
      #6106036 - 09/28/13 02:05 PM

http://www.manualslib.com/download/342383/Zhumell-Tycho.html

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rdandrea
Carpal Tunnel
*****

Reged: 06/13/10

Loc: Colorado, USA DM59ra
Re: Zhumell TYCHO 254 new [Re: BigC]
      #6106248 - 09/28/13 04:11 PM

Sounds like a Jones-Bird design. Google it. Not an easy scope to collimate and not a design that is known for good optical performance.

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GlennLeDrew
Postmaster
*****

Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: Zhumell TYCHO 254 new [Re: rdandrea]
      #6106316 - 09/28/13 05:01 PM

That image does show coma, of pretty uniform degree and orientation. The system is very far from collimation. Reversed lens elements by themselves will not necessarily be the culprit for this aberration.

When adjusting the secondary alignment, I gather the entire unit housing the mirror and lenses tilts? If so, I wonder if there is a means to alter the tilt of the secondary mirror by itself, with respect to the 'Barlow'.

Do you have a laser collimator? Place a white paper projection screen surrounding the laser's exit hole, with the smallest hole in the paper possible. Place a small mirror beside the secondary assembly so that you can sight up into the focuser tube from the front of the scope, and thereby observe the reflected spots on the white surface. I should think that the 'Barlow' lens surfaces can send back sufficiently bright reflections, at least in dark conditions. Ideally, all spots should fall on the laser's exit aperture. The more dispersed the reflections, the poorer the alignment.

The brightest spot by far will be that returned by the primary. Each of the four lens surfaces should send back a very much dimmer spot, with the possibility of one or more being enlarged somewhat due to the curvature of the surface and additional refraction upon return.

It might be better to do this with the secondary adjustment screws well loosened, so that you can wiggle the secondary assembly by hand and observe the relative movement and disposition of the spots. If there is no point at which the group all occupy at least nearly the same place, after further adjustments if the primary as well, things are likely out of whack with that secondary housing.


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Muffin
member


Reged: 09/27/13

Loc: Pinelands-near Cape Town,South...
Re: Zhumell TYCHO 254 new [Re: BigC]
      #6106845 - 09/29/13 01:33 AM

Good morning - many thanks for your posting -- I already have this manual and its not particularly useful - nothing about collimation or whether parabolized or spherical and nothing about the "barlow lens" attachment. I liked the one statement in it " eyepieces intended for external use only" !!!

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Muffin
member


Reged: 09/27/13

Loc: Pinelands-near Cape Town,South...
Re: Zhumell TYCHO 254 new [Re: rdandrea]
      #6106850 - 09/29/13 01:46 AM

Quote:

Sounds like a Jones-Bird design. Google it. Not an easy scope to collimate and not a design that is known for good optical performance.




Yes this is the opinion offered by someone else on another forum and after goggling it it does indeed look like its a Jones-Bird design :-((( and as you mentioned the general trend was that it is not easy to collimate and is not a popular design - this will also explain why apparently so few were manufactured - its basically a flop. Anyway I shall battle on in the homes that it can be "saved".


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Muffin
member


Reged: 09/27/13

Loc: Pinelands-near Cape Town,South...
Re: Zhumell TYCHO 254 new [Re: GlennLeDrew]
      #6106870 - 09/29/13 02:17 AM

Quote:

That image does show coma, of pretty uniform degree and orientation. The system is very far from collimation. Reversed lens elements by themselves will not necessarily be the culprit for this aberration.

When adjusting the secondary alignment, I gather the entire unit housing the mirror and lenses tilts? If so, I wonder if there is a means to alter the tilt of the secondary mirror by itself, with respect to the 'Barlow'.

Do you have a laser collimator? Place a white paper projection screen surrounding the laser's exit hole, with the smallest hole in the paper possible. Place a small mirror beside the secondary assembly so that you can sight up into the focuser tube from the front of the scope, and thereby observe the reflected spots on the white surface. I should think that the 'Barlow' lens surfaces can send back sufficiently bright reflections, at least in dark conditions. Ideally, all spots should fall on the laser's exit aperture. The more dispersed the reflections, the poorer the alignment.

The brightest spot by far will be that returned by the primary. Each of the four lens surfaces should send back a very much dimmer spot, with the possibility of one or more being enlarged somewhat due to the curvature of the surface and additional refraction upon return.

It might be better to do this with the secondary adjustment screws well loosened, so that you can wiggle the secondary assembly by hand and observe the relative movement and disposition of the spots. If there is no point at which the group all occupy at least nearly the same place, after further adjustments if the primary as well, things are likely out of whack with that secondary housing.




Morning - many thanks for your posting..... as you may see from comments it appears to be a Jones-Bird ( Ive also seen it called Bird Jones so Im not 100% sure at the moment which it is ) but irrespective very difficult to collimate and not famous for its optical quality. Unfortunately it is not possible to alter the tilt of the secondary mirror with respect to the "barlow"- Ill check again-just to make sure -but it appears to be all one solid unit so the orientation with respect to one other is fixed. I do have the loan of a Zhumell laser collimator but not sure if its working - someone ( not me) has managed to get one of the button batteries stuck at the bottom of the tube that contains the three batteries necessary to power the laser-not sure how Im going to get it out without causing damage but will have another go at it since it looks like the conventional way of collimation is no good. I suspect the stuck battery is probably flat. I did try collimation it as best possible and trying final collimation on a bright star but didnt really get any worthwhile improvement.Apparently the laser collimator had been used by the previous owner but had never got rid of the "coma" and was one of the reasons why the scope was used so seldom and finally disposed off.
Anyway I am making "progress" - pity Zhumell either no longer exists - cannot find an email address for them, so tried one of the agents selling Zhumell equipment but the email was returned as " unable to deliver it" so it looks like they also have a problem. Found another Zhumell supplier yesterday so emailed them but I strongly suspect its the same "unable to deliver" company with a different name! If all fails eventually Ill have the mirror parabolized - ( something I last did about 50 years ago!) but I have an expert telescope making friend but unfortunately he is so busy making telescopes I dont know what the timeline will be. Best wishes, Greg


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rdandrea
Carpal Tunnel
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Reged: 06/13/10

Loc: Colorado, USA DM59ra
Re: Zhumell TYCHO 254 new [Re: Muffin]
      #6106983 - 09/29/13 06:25 AM

No luck with http://www.zhumell.com/contact-us/ ??

Try warming the barrel of the collimator gently with a hair dryer. It might expand enough to get the stuck battery out.


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Muffin
member


Reged: 09/27/13

Loc: Pinelands-near Cape Town,South...
Re: Zhumell TYCHO 254 new [Re: rdandrea]
      #6108679 - 09/30/13 04:49 AM

Quote:

No luck with http://www.zhumell.com/contact-us/ ??

Try warming the barrel of the collimator gently with a hair dryer. It might expand enough to get the stuck battery out.




Morning --- well I spent several hours battling yesterday trying to get the battery out and failed, so reasoned that since it was now essentially useless I would take the collimator apart - of course loosing its collimation (if in fact it had ever been collimated!) and it turned out to be a very easy task as the unit is so simple in construction. Anyway got the battery out - it was so old it had corroded and green "gunk" was holding it in the tube. Cleaned that all up and can even now hear the microswitch for switching the laser unit "on" working so tomorrow will get three new batteries and hopefully Ill have a non-collimated collimator! I have no idea when it was last used by the owner - I suspect a VERY long time ago !

Ive also been reading up quite a lot on the Jones-Bird system and am encouraged by what I read and at the moment I feel pretty confident that I can get it to perform well enough for my purpose - prime focus newtonian photography of high altitude satellites. I do expect coma because Im using a relatively wide field of view but at least the coma should now behave like coma. The software used to process the images has no trouble with coma or other distortions - very fancy piece of software written for positional determination of satellites and used by the ISON Network and gives positions to sub-pixel accuracy. Anyway many thanks to you and the other contributors for the possibility it was a Jones-Bird system - something I was not aware of previously....
Enjoy your day
Best wishes
Greg Roberts


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GlennLeDrew
Postmaster
*****

Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: Zhumell TYCHO 254 [Re: Muffin]
      #6109290 - 09/30/13 01:32 PM

I trust you know to check the collimator's collimation by spinning it on a V-block...

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Muffin
member


Reged: 09/27/13

Loc: Pinelands-near Cape Town,South...
Re: Zhumell TYCHO 254 new [Re: GlennLeDrew]
      #6111679 - 10/01/13 06:19 PM

Quote:

I trust you know to check the collimator's collimation by spinning it on a V-block...




Hi Glenn - Many thanks for your input - hadnt thought of using that way - was going to put the collimator in my metal lathe's chuck ( gently!) and then slowly rotate the lathe chuck by hand and with a thin pointer resting on the lathe bed align the collimator by making sure it was concentric with the lathe chuck - ie no obvious deviation from the contact with the pointer - easier to do than describe ! I put in new batteries today ,after having to disassemble the Zhumell collimator to get the dud corroded battery out, and all now works 100% - nice bright red beam ( of course not looking directly into it!) - so hopefully over the course of the next few days I will be able to get into my workshop and do the collimation of the telescope itself. Best wishes, Greg.


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orlyandico
Postmaster
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Reged: 08/10/09

Loc: Singapore
Re: Zhumell TYCHO 254 new [Re: Muffin]
      #6112050 - 10/01/13 09:46 PM

Instead a of V block, four nails in a block of wood is an option... An option I will exercise when I get my collimator...

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pftarch
professor emeritus


Reged: 09/21/07

Re: Zhumell TYCHO 254 new [Re: orlyandico]
      #6112950 - 10/02/13 11:25 AM

Any thoughts of removing the barlow and seeing what happens? (Is it easily "unscrewable"?)

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pftarch
professor emeritus


Reged: 09/21/07

Re: Zhumell TYCHO 254 new [Re: pftarch]
      #6112967 - 10/02/13 11:32 AM

Also......

It may be advertised at 600X, but I don't believe any claims over 2X the aperture in mm, (508X max), and, at least where I live, getting a clear view at 500X with my 10" is a tall order. My atmosphere conditions seem to dislike anything over 250X with an occasional, rare, fleeting, pristine view over 300X. (But those nights are like a once every three year occurrence for me.)

I call it a great night if I can go over 250X at all......

Peter T.


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Muffin
member


Reged: 09/27/13

Loc: Pinelands-near Cape Town,South...
Re: Zhumell TYCHO 254 new [Re: orlyandico]
      #6118413 - 10/05/13 02:17 AM

Quote:

Instead a of V block, four nails in a block of wood is an option... An option I will exercise when I get my collimator...




Many thanks for the suggestion - when I finally get a chance to look at the telescope/collimator I will see what produces results so all suggestions welcome at this stage. Have a god weekend! Cheers Greg


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Muffin
member


Reged: 09/27/13

Loc: Pinelands-near Cape Town,South...
Re: Zhumell TYCHO 254 new [Re: pftarch]
      #6118421 - 10/05/13 02:30 AM

Quote:

Any thoughts of removing the barlow and seeing what happens? (Is it easily "unscrewable"?)




Morning - yes I did remove the B-J corrector and tried the scope but focus was right on the edge of the telescope tube- had to lower the secondary and push up the mirror as much as possible on the three adjustment screws. Tried it in daytime on my most distant terrestial object - a neighbours TV dish but , from experience I know this is not focus infinity so will have to go in even closer. I could get focus on the dish -looked nice but of course a daytime object is not as demanding as a stellar image!. I thought using the scope at f/4.7 suited my purpose better so was going to machine a new eyepiece/camera holder. Then discovered it was a B-J setup and spherical primary so decided it was really a waste of time trying to use at f/4.7. Then we had the FALCON 9 launch and my life has been chaos since - check my name - Greg Roberts on Google with subjects such as Falcon UFO and satellite tracking and that will give an idea of the load of work here. Currently processing something like 1300 images I took of a transit of the 20 objects from the CANOPUS launch and trying to idenify all the objects seen - but thats OT here and too long a story but suffice all chances of playing with telescopes are out at the moment and my next space mission is the JUNO earth flyby on the 9th Oct after which hopefully I can get back to the Zhumell. Cheers Greg


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