Lost in Space? The TELRAD Solution

[@grortyphx]

Simple, clear, precise....great stuff, Martin!

[@martinsastrophotography]

Thanks. Glad you liked it. Clear Skies!

[@GaryEasonFlightArtworks]

Very clear, as always. I have a Telrad on my 150P Newtonian. Rather than use the sticky pads on the base to attach it to the OTA - possibly misalign it, and certainly make the base awkward ever to move - I attached some cheap little real earth magnets to the base. They now hold the base very firmly on the tube however it is pointing - but are also very easy to detach/move/whatever.

[@martinsastrophotography]

Thanks Gary. Nice idea with the magnets! The worst thing about the sticky pads is when you decide to try to remove them!!! Leaves a horrid sticky mess on the OTA. Clear skies.

[@kennethschroeder2789]

Gary. Do you have a photo or a detailed description of how and where you attached the magnets to the OTA and the Telrad? I just picked up a used Meade LX 90 scope and want to attach a Telrad in a similar way.

[@memsanders8462]

Excellent video. You cant make it more simple than that. Impressive modifications on the Tellrad. Well done. I ordered one. Thanks.

[@martinsastrophotography]

Thank you! Enjoy your Telrad. Clear skies.

[@chetwood6517]

Thanks! Well done😀

[@Jkaterchannel]

Suscribed. I like how you explain things clearly and without theatrical. Well produced video.

[@martinsastrophotography]

Thank you! Much appreciated.

[@mikeleahy5283]

I had a telrad on my 8” dob loved it

[@douglassmith1215]

Another trick to fix the "lost in space" program is to use the guidescope camera as a kind of electronic Telrad. As you mention in you excellent PHD2 video, you don't actually need a very long focal length guidescope. The 120mm ones (like from ZWO) are quite suitable (except for an SCT). If you combine this with a IMX174 chiped guide camera, you get a very wide field of view (because the 174 chip is quite big, 13.3mm diagonal). When finding alignment starts, I use the planetary imaging program that comes with ASI Studio. There's even a bullseye you can overlay. This assumes you have aligned the imaging camera and guide camera fairly precisely. A big advantage of this technique is you can do it indoors, where it's warm, if you've set up remote operation. The Telrad requires that you are physically next to the scope.

[@martinsastrophotography]

Interesting idea. For me the Telrad wins out over the approach you describe because the field of view (of your eyes!) is so wide. But yes, it involves being right next to your telescope. The ultimate progression for me is plate solving, which will be the subject of an upcoming tutorial. Clear Skies! (And they actually have been lately!!)

[@douglassmith1215]

@@martinsastrophotography Yes, great weather lately here in the UK. Looking forward to your plate solving video. I've been using All Sky Plate Solver lately. It makes a world of difference.

[@edjones3390]

Always wanted a telrad but was concerned with dewing problems - resister cluster is a great DIY idea !

[@martinsastrophotography]

Yes, it’s a great upgrade! Sorts the dew completely.

[@MasseyLee]

great tip.thanks

[@SmeeUncleJoe]

I love my Telrad. Unfortunately the gentleman who gave us it has passed on and left an affiliated couple to carry on the business. i ended up buying a replacement one and it was very jumpy in terms of intensity. The vendor had to go through quite a few before we found one operating relatively smoothly to honor the warranty. It wasn't dirty pots on the control either as I cleaned mine and it still would jump around. Not sure what that is about.

[@kennethschroeder2789]

Martin. Thanks for the tip on dew control. Could you add a comment or two that describes a bit more about the dew control circuit? Maybe include an online source for the 12V plug and what resistors you used for your modification.

[@martinsastrophotography]

It’s just a 5.5x2.1mm socket mounted in the housing and connected to three high watt rating axial resistors soldered together in parallel. (I will check what the resistor values were). These are glued in place behind the glass window near the bottom to minimise obscuring the view. I power it from 12V. Works a treat.

[@dettie1948]

I use what I call the "Duffy" technique, (named after a much appreciated collegue), and on the first alignment star slip the clutches and align manually rather than use the hand controller, this takes out any minor alignment issues with the mount and enhances accuracy (in my experience)

[@astrotechnique1]

Use nina. Slew and center tarhet. That's all you need to do.

[@martinsastrophotography]

I totally agree, but the Telrad is still great for folks that have not yet connected their mount to a computer, or have done so buy have not yet discovered the wonders of plate solving. For me it was a great aid for quite a while.

[@mesenteria]

Shouldn't the star field move in the final demo? The Telrad is firmly affixed to the scope, and the scope isn't showing the alignment/guide star. One should slew the telescope in the direction suggested by the Telrad display, and then the item should appear in the field of view. But, during the slewing, the Telrad's view should show the starfield moving to get to the center of the Telrad reticle. Have I missed something?

[@martinsastrophotography]

No. You must first get your main telescope optical train and camera/eyepiece centred on a suitable bright star. You then adjust the red concentric rings on the Telrad until they are centred on the same star. Once that is done, the Telrad and main optical train are aligned….that is to say, when the Telrad rings are centered on something, the optical train will be centered on the same thing, so you can then use the Telrad to get you telescope pointing at your object. Does that help?

[@mrh9635]

I've just attached mine to my 9.25 SCT to replace the stock Celestron 6x30 finder. Can't wait to use it. I'm intrigued by your dew solution for it and would like to know if it can be done without too much expertise? If not I'll have to settle for making some sort of cardboard hood myself.

[@martinsastrophotography]

Essentially I added a DC jack socket to the side for a 12V DC supply. I then wired the socket to three 10ohm, 10Watt rated axial resistors soldered in parallel to form a triangular cylinder than sits nicely against the back of the glass window. I powered it from a dew heater controller set to about 40%. You can probably set it lower than that. If you do implement this, don't turn it up too high as the resistors will burn out. Their combined resistance is 3.33 ohms, so at 12V you will get a total current of 3.6 Amps (I=V/R), 1.2 Amps through each resistor which will dissipate 14.4 Watts (P=I²R) in each resistor and they are only rated 10Watts so they will fry. Run them at about 4.8 Volts (40% of 12V) and you get a total current of 1.44 Amps, 0.48Amps through each resistor, giving 2.3 Watts of dissipation per resistor, which is fine. Hope this helps!

[@mrh9635]

@@martinsastrophotography Fascinating. Trouble is I still haven't got to grips with regular dew heaters so still too daunting for me at present. I was thinking of a cordless heat gun for the time being but worry it might warm the mirrors unintentionally.

[@martinsastrophotography]

@@mrh9635 if your Telrad dews up, your telescope probably will too without a dew heater. What specific concerns do you have with dew heaters?

[@mrh9635]

@@martinsastrophotography I just got back into astronomy and I only have a basic dew shield for my 9 1/4 SCT. I just want a powered solution without having to buy an alternate power source. It isn't clearly stated anywhere I look, so I'm not sure my Celestron Lithium powertank and my AVX mounts ports can power the scope and a dew heater simultaneously.

[@ericnicholson870]

Is it easier to use than a red dot finder? And is a conventional lens finder more difficult to use?

[@martinsastrophotography]

I prefer it to red dot or conventional lens finder. It’s important to prevent dew building up on the glass plate. I added some resistors powered from 12V to do this.

[@hornsby5533]

I am looking for a solution for my Zeiss Diascope 85. Unfortunately, the housing is not cylindrical, but rather it resembles a truncated cone.

[@martinsastrophotography]

The Telrad does not have to be mounted on the telescope. It can be mounted next to the telescope. It just needs to be pointing in the same direction (approximately) and be rigidly mounted to the same dovetail as the telescope. I hope this helps.

[@martinezq1]

Why it is so long ?

[@GaryCameron]

Why is the telerad so big compared to the Rigel?

[@martinsastrophotography]

Sorry, I don’t understand your question. Rigel is a star.

[@mjkeaton1]

What would be the process for using a Telrad for polar alignment? Would I align the Telrad so a bright star is centered in both the Telrad and the telescope, then align the telescope to Polaris using the Telrad? Or is there a better way? Thank you!

[@martinsastrophotography]

Hi Michael. You cannot use a Telrad for polar alignment because it is mounted on the telescope. Polar alignment is not an alignment of the telescope but is an alignment of the Right Ascension axis of a German equatorial mount that enables the Earth rotation induced motion of the sky to be corrected by rotation of the Right Ascension axis alone (either by hand or driven by a motor in the case of a tracking mount). Check out my other videos for more details. What mount do you have?

[@mjkeaton1]

@@martinsastrophotography Thanks, Martin. I am buying a second-hand Celestron AVX mount from a friend. He has used it very successfully with a William Optics ZS-81 refractor. I'm new to astrophotography and I plan to follow his example with the same telescope. Getting good polar alignment is my main concern. But I won't have all the equipment until later in September. Just trying to understand and prepare at this point. BTW, my friend did recommend the Telrad so I plan to get one.

[@martinsastrophotography]

@@mjkeaton1 Hi Michael. Sounds exciting. The Telrad will be very useful for star alignment but not for polar alignment. The Celestron AVX has All-Star polar alignment and SkyAlign for star alignment. Are you happy with the difference between polar alignment and star alignment or would you like me to explain?

[@mjkeaton1]

@@martinsastrophotography So let me try to explain and correct me where I"m wrong. Polar alignment aligns the polar axis of the mount to the North Star so that objects can be accurately located using the RA and Dec of that object. Star alignment aligns the telescope to an alignment star so that the star is in the center of the field of view. Once that is done, I can use the Telrad to center on any other star and have that star be right in the center of the field of view. So how does the Telrsd help align on dimmer objects that the naked eye can't see? Do I center on the nearest bright star to the object, then adjust the telescope? Thanks very much for your assistance.

[@martinsastrophotography]

@@mjkeaton1 A good effort Michael but not quite there. Polar alignment aligns the Right Ascension axis of the mount so that it is parallel to the Earth’s rotational axis (which is the line joining the North Celestial Pole to the South Celestial Pole). The North Star (Polaris) is close to the North Celestial Pole but is far enough away from it that the difference matters in Astrophotography. Polar alignment has nothing to do with locating objects in the sky. It is just so that a motor drive on the RA axis running at the exactly correct speed will cause the telescope to track any object as the Earth rotates. Star alignment is performed after balancing and polar alignment have been completed and the mount has been placed in the “home position “ and the RA and Dec clutches have been locked. Star alignment uses 1, 2 or even 3 known stars which the mount is driven to point the telescope at so that the mount “knows” where the sky is relative to the home position. Once star alignment is done, a Goto mount can be commanded to point at any object in its database and it should be able to move to point your telescope at it (assuming it is above the horizon!). The Telrad is very useful when performing star alignment. Once it is aligned with the telescope you can the slew the mount to a bright known star and centre it in the Telrad in order to also get it into the telescope’s much narrower field of view. There’s a lot to take in here I know, but after a while it becomes second nature. Here is a sequence: 1) assemble mount with rough orientation to North. 2) Assemble telescope and camera etc.. onto mount. 3) Balance in RA and Dec. 4) Polar Align. 5) Move to home position and lock clutches. 6) Star Align. 7) Start tracking at sidereal rate. 8) Command a Goto to your desired object. 9) Have fun looking at or photographing it!!!

[@fidelet]

Hi! My lightbridge has a GSO Red Dot Finder. Should I replace it with a telrad? Is it a better finder or there is no much difference? Thanks and clear skies

[@martinsastrophotography]

Hi Fermin. I have not used a red dot but a web search of comparisons suggest the Telrad works better than the red dot finder, with the only negative point on the Telrad is that it is larger. I suggest you check the size of the Telrad and see if it would fit comfortably on your telescope. If so, I would go for a Telrad.

[@nickwhite2286]

The nice thing about the Telrad that he didn't go into is the 3 concentric circles. These circles are 4 degrees, 2 degrees, and 1/2 degree in width. This will be really helpful in your Lightbridge when you are star hopping because now you can measure approximate distances using the Telrad to help you better star hop - some star map apps will even show you how the Telrad circles should be placed to help you find a target that is not bright enough to see with the bare eye.

[@jimjebavy633]

The TELRAD my lens came loose I'm going to glue the lens back, my ? is the crown up or down?

[@martinsastrophotography]

Hi Jim. Assuming by 'crown' you mean the dome of the lens, it should be 'up'.

[@josegiovanni8695]

Its compatible with Celestron 8 SE?

[@martinsastrophotography]

Yes, it fits on any cylindrical telescope tube using adhesive pads.