Halo artifact troubleshooting on Esprit ED80 and lens cleaning safety

Equipment Refractors Optics Artifacts Cleaning Help Needed Troubleshooting
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Lucas Jacobson avatar
Lucas Jacobson avatar

I’m looking for some troubleshooting help with my Esprit ED80. I have this strange halo artifact on mid to bright stars (see attached image). If I rotate the image train, the defect follows the scope, so I know it’s there, and it is equally present in all filters and without filters. I don’t see any obstruction or anything, but I’m nervous to remove the lens set itself to thoroughly clean it.

Can anyone give me their best guess on the source of this, and secondly, can anyone tell me if its okay to take the lens group as a whole off the scope to clean it as long as I don’t seperate the individual lenses from each other? Thank you in advance for your help!

HaloPrism.png

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andrea tasselli avatar
andrea tasselli avatar
Look something is protruding into the light path. And, yes, it's fine to remove the lens' cell and clean the inner surface and to check what's going on.
Lucas Jacobson avatar
Lucas Jacobson avatar

Thanks Andrea. I’ll give it a go.

Brian Puhl avatar
Brian Puhl avatar

You can remove the lens cell and clean it. I’ve done this on a few Esprits now. There is a video guide somewhere online from Skywatcher that demonstrates the process. I can’t for the life of me find it now. Just make sure you remove the correct screws! Putting everything back together will require assistance from your friend, as getting the washers to line up while installing the screws is nearly impossible alone.

One of my esprits is starting to get stars like that as well and I need to investigate.

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Brian Puhl avatar
Brian Puhl avatar

You can remove the lens cell and clean it. I’ve done this on a few Esprits now. There is a video guide somewhere online from Skywatcher that demonstrates the process. I can’t for the life of me find it now. Just make sure you remove the correct screws! Putting everything back together will require assistance from your friend, as getting the washers to line up while installing the screws is nearly impossible alone.

One of my esprits is starting to get stars like that as well and I need to investigate.

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Lucas Jacobson avatar
Lucas Jacobson avatar

Thanks Brian. I’ve got a support email into Sky-Watcher as well. Does your issue show up as hourglass halos on stars that are all aligned in the frame or something different?

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Lucas Jacobson avatar
Lucas Jacobson avatar

I finally got to the bottom of the issue with the Esprit 80. I sent the scope to Tony Costanzo, who did a great job getting everything collimated within the triplet group and aligning everything. This gave me a significant decrease in star size (25 to 30% reduction). However, the hourglass halos were still there on the brightest stars. I then looked in the objective lens and noticed a slight difference in reflectivity of the glass around the edge of the objective lens. A grabbed a random m74 to m63 ring I had a place it in front of the objective lens. The halos disappeared. So, I cut out a ring from a piece of construction paper and taped it to the outer ring of the scope so that it covered the outer 1mm or so of the objective lens. Problem solved. I’ll 3D print the appropriate ring so that it is cleaner than paper and smooth to avoid micro diffraction spikes. If anybody else has this problem, the solution may be just as simple as turning your ED80 into an ED78.IMG_5214.jpeg

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churmey avatar
churmey avatar

Hi Lucas,

The problem with most Esprit 80’s is the retaining ring slots are barely exposed just behind the main aperture cover (the one that has markings on it). You can buy a 3.5” O-Ring, cut it to size, and it fits perfectly in a slot right behind the aperture cover and just in front of the retaining ring. Basically it creates a 79mm aperture mask and the O-Ring is a very smooth transition. I did this to my Esprit 80 (that I purchased used) and it fixed the issue completely. Mine not only had the same flare type as yours, but all of my flares were in the same direction throughout the whole frame. If interested in the O-Rings that I purchased, just let me know and I can shoot it to you. Good luck, hope you can rectify your issue.

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