Edmund 4.25" Palomar Jr. Newtonian

Image of Edmund Palomar Jr focuser and finderMy oldest scope is an Edmund Palomar Jr (Pal Jr). It’s a 4.25 inch (108mm) Newtonian reflector on a German equatorial mount. It’s been in regular use ever since I got it in 1973. These days I use it primarily for solar observing using a Baader AstroSolar Safety Film aperture filter. I also use it to compare views with my Zhumell 10 inch (250mm) Dobsonian (Z-10) and to verify what a smaller aperture can show under washed-out skies.

The optics on the Pal Jr are surprisingly good, consistently showing picture-perfect diffraction patterns. It gives great views of the planets and splits η Orionis whenever the seeing is decent. In dark skies, it’s shown me most of the Messier objects and plenty of NGCs. In washed-out skies it still gives good views of double stars, open clusters, the brighter globular clusters (without any hints of resolution), and the brighter nebulas (M27, M42, M57), but apart from M31 it is exceptionally hard to see any galaxies with it. I’ve made a point of including observations with the Pal Jr throughout Washed-out Astronomy to balance the Z-10 view with a smaller aperture view.

The most interesting thing about the Pal Jr is that it was hit by lightening some years ago….

Lightening 1, Telescope 0

In 1991 I kept the Pal Jr in a light-weight shed, the kind commonly used to keep lawnmowers and gardening tools. During a particularly ferocious thunderstorm that summer, lightening scored a direct hit on the shed. Amazingly, nothing caught fire although the roof and one wall of the shed were heavily damaged. My immediate concern was water damage, but the Pal Jr was kept at the opposite side of the shed and was tightly capped, so the inside of the scope stayed dry. The outside of the tube had a small scorch mark near the bottom (mirror end) of the tube, but I didn’t worry about it, until I looked down the telescope at the mirror. The mirror was covered with a “lightening pattern” across most of its face. It looked as if static electricity had danced across the aluminum layer, melting the aluminum into a beautiful pattern—beautiful but unfortunately useless for astronomy.

So I sent the mirror off to be re-coated (I wish I had taken pictures of it, but I didn’t think to do it at the time). But the re-coater called me to report that the pattern was actually melted into the surface of the glass, and the mirror would have to be re-ground. And so I paid to have that done (I’m not an ATM-kind-of-person) and a month later had my mirror back. The new figure was just as good as the old one, except the focus was shorter, about 1004 mm (instead of the original 1080 mm).


Pal Jr showing the front end mods

While the Pal Jr is now considered a “classic” telescope, I’ve always treated it as a working telescope and have never hesitated to improve it. The modifications I’ve made so far are:

  • The original f/10 mirror has been re-ground (courtesy of the lightening strike) to f/9.3. This also forced me to move the primary mirror mount about 3 inches forward in the tube. I also center-marked the primary (the original primary was not marked).
  • The original focuser (which had pressure-tabs to hold the eyepieces in place) has been replaced with a focuser that uses a set screw to lock the eyepieces in place. This allows me to change eyepieces without throwing off the telescope’s aim.
  • The original rectangular secondary mounted on a single-stalk has been replaced with an elliptical secondary mounted on a three-vane spider. I needed to do this because the new focuser couldn’t hold the original the single-stalk diagonal.
  • I flocked the upper end of the telescope tube with Protostar flocking material.

These modifications are all visible in the photo above.

Overall Review

Pal Jr mount and scopeThe optics on the Pal Jr are top-notch, as shown by the consistently clean Airy disk it shows during star-tests and its consistent ability to split doubles near its Dawes’ limit (1.1 arcsecs). The long focal length makes the views coma-free. Unfortunately the mount is nowhere near as good as the telescope. It vibrates a lot and the motion on both axes doesn’t have enough stiction, so when the scope is perfectly balanced a slight breeze is enough to move it around. The mount has screw-knob friction brakes on both axes, but tightening them even a little bit makes the vibration significantly worse. I plan to one day re-mount the Pal Jr as a Dobsonian, which I think would make it a great telescope.

Despite these complaints, the Pal Jr has shown me many sights and it is still a good performer. The mount legs disassemble and assemble quickly, making it easy to throw in the car and set up. The silly straps used to attach the tube to the mount actually work pretty well, and make it easy to rotate the focuser to a convenient viewing angle. The Pal Jr still wows both kids and adults when they see Jupiter, Saturn, the double cluster or the Orion nebula through it. It provides great views of the Sun using the Baader filter, and most importantly, I still enjoying looking at the skies through it, even washed-out skies.



Pal Jr.

Great story here Washed Out! This is a wonderful scope with a colorful history! My neighbor had a 6" inch version of this scope when I was a kid and it was the first scope I ever looked through! A number of years back I was doing a outreach program and someone walks up to me and asked if I could spare a few minutes to help them with their scope so their 12 year old son could use it. Low and behold it was a Pal 4.5"  in excellent shape too! They would not sell it to me!  Anyways after a little tune up they are up and running and the views were good. Everything was orginal on it - even the pressure fit focuser - cool!
My older brother had a Edmund 3" ALT/AZ Reflector purchased about 1969. Neat scope with sturdy wooden legs and mount. I wish I had it ! Had my first view of M13 through this scope.
Your story and write up is well done and a fun read. Thanks for sharing it with us!
Again this scope is a gem indeed. I will think twice about setting up in questionable weather too!

4.25 Inch Mt. Palomar Jr.

I have one of these telescopes! Years ago I enjoyed it very much. However, about 5 years ago, I moved and I did not pack the eyepeices with the telescope. Big Mistake!
I have been unable to locate the eyepeices. I will continue to look, but in case I do not succeed.,

Can you tell me where I might find at least a low power eyepeice that I could buy while I continue to look for the others?

Any help you can give will be appreciated.
Thanking you in Advance,




You can easily get eyepieces on line at any one of these:

Agena Astroproducts
I've shopped at all three and had good experiences.  Although their Google Ads may appear on this site from time to time, I have no personal affiliation with any of them.

I would suggest getting a basic Plossl eyepiece in a 20 to 28mm focal length to have a decent, low power eyepiece.  Your next eyepiece can be a basic Plossl in the 9-14mm focal length range.  Don't go below 9mm or the eye relief gets too short to be comfortable (even 14mm will be tight if you need to wear glasses).  You can find decent Plossl eyepieces without hurting your wallet at any one of these shops.

I hope this helps,

Washed-out Astronomer


That's my first scope, too! (If you don't count the Sears and Roebuck 3-incher with the bad optics I had when I was 7). I'm a high school Science teacher now, and I'd like to get the scope back it operation. About 10 years ago, I used the diagonal mirror to project a solar image on a distant campus building when there was a solar eclipse, and I misplaced the diagonal somewhere in a box in my garage.

I've written to Edmund, but they can't provide a secondary.

Which 3-vane spider did you get?

My latest idea is to replace the shaky mount with one similar to the Meade Autostar Mount. The telescope is light enough so I might get that clock drive I've always wanted for it, and it would be computerized now.

--- Steve >>>>



I had a really hard time finding a replacement spider that fit the rather narrow tube of the Pal Jr.  The only one I could find was at Destiny optical company. But I never actually bought the Destiny spider+diagonal because through a friend of a friend I found someone who sold me an old three-vane spider that fit my scope. 
You might want to also try asking on Cloudy Nights in their ATM forum. 
If you get yours on a goto mount, I'd love to see a photo of it.
-- Washed-out Astronomer

Secondary Size


I was pleased to read your story about this telescope. My brother-in-law found one of these in the attic of the rental property he owns. He gave it to me and I replaced the missing secondary and had the primary recoated. It works swell. Now I'm looking to upgrade the focuser to a JMI RCF-mini1. As you point out, this means replacing the stalk with a spider, and I'm planning to order a Destiny curved vane spider.

I'm wondering what size secondary you have. Currently on my stalk I have a 0.75", but I've always wondered if that's too small, and I'm considering a 1" secondary this time. What size secondary did yours come with, and is that what you have in it now?

Thanks very much,
Mark Gilbert
Saint Paul, Minnesota

Secondary Size: Go for 1 inch

The original secondary (the one on a stalk) is a 1 inch wide rectangle that is seen as a 1 inch square when viewed through the draw-tube. 
I replaced it with an elliptical secondary that is also 1 inch wide, so it appears as a 1 inch circle when viewed through the draw-tube. I've not noticed any vignette or fading near the edges with this configuration.
This makes me think you really should go for the 1 inch secondary when you modify your scope.  But to be sure, I recommend you use the free NEWT software tool to check the ray traces for your configuration.  That should show clearly which diagonal size is best.
Washed-out Astronomer

Edmund Mt. Palomar

How I miss mine. Had to store it in a friend's basement, some 20 years ago. His kids threw it out. I think it was 1968 when my parents bought mine for me.

Great article

Great article. I got out a 50 year old Palmar Junior that was my Dad's. Used a laser to align it and bought some new eyepieces (Teleview 24mm and a 9mm). I have been completely shocked at how good it is. The focus rack & pinion wobbles a bit though - so I want to replace it. Which one did you use? Thanks, Paul

Replacing the focuser

The challenge in replacing the focuser on the Palomar Jr is that the stock focuser also anchors the single-stalk mount for the secondary mirror.  I was not able to find a replacement focuser that would also hold the single-stalk secondary, and I doubt you will (unless you can find one from another Palomar Jr).  So replacing the focuser also entails installing a new holder for the secondary.  I use my Palomar as a "secondary" telescope, so I didn't get a fancy focuser: I bought a run-of-the-mill focuser from Orion. Even though I didn't spend much for it, it is pretty smooth compared to the original focuser and it has a set screw (instead of the pressure tabs), so I can change eyepieces without accidentally changing the telescope's aim.  For the secondary mount, I got a three-vane spider used from someone on Cloudy-Nights.
Good luck!  Washed-out Astronomer.

I've had my 4 1/4" Palomar since 1969

I was 13 when I got it. It was my first scope and a great introductory one at that! That's because it was lightweight and easy to disassemble and reassemble and it had the equatorial mounting, so I could learn how to use setting circles.

For a long time, I wanted to upgrade to a 6" and then an 8" scope. It never happened. Then in 1997, after being a really good boy for so long, I bought a 10" Meade Starfinder Newtonian with an equatorial mount. It also came with a Magellan I computer and a clock drive. This scope was huge next to the 4 1/4". The only things that were great about the 10" were the optics and the stand. One of the straps (that secure the scope to the mount) broke the first time I went to use it. The rack and pinion focuser was jerky compared to the one on the 4 1'4". The stand on the 10" would stop wobbling much quicker than the 4 1/4". The views were so much brighter than the 4 1/4".

I have really bad arthritis in my right hip and I can't disassemble the 10" anymore, being that I can't really walk without a crutch. I am selling the 10" and started using the 4 1/4" again. This is after I started using binoculars a few times and I told myself, "this isn't cutting it". I need a scope.

I'm using a 15mm eyepiece I bought for the 10" with my 4 1/4". There's a rubber eye cup which keeps my eye at the proper distance from the eyepiece and the cup also blocks out light. I'm keeping that eyepiece. It's the primary one I use when doing sky sweeps. I sweep along my prime meridian to look at anything interesting that pops into view. I don't need deep space catalogs or need to use the setting circles. I've been doing this for years. After all, some of the best objects are (in my opinion) are different colored stars and binaries and other packed starfields. A lot of these aren't in catalogs. I pretend like I'm an earlier astronomer that had to discover the wonders of the cosmos by myself. I still have the sense of wonderment I had as a 13 year old.