ToupTek Astro offers some of the most affordable astronomical filters on the market. But, when it comes to deep-sky imaging, does the price point impact their performance? Let’s dive into the real-world evaluation of ToupTek’s 2″ LRGB and SHO filters , focusing on one crucial aspect: focus performance.
User Introduction
Meet Kehuajin, an avid astronomy enthusiast and astrophotographer with two years of experience. He’s also a popular video creator on Bilibili, where his tutorials and science content have garnered ove r 15 milli on views and earned him a dedicated following of over 160,000 people. Kehuajin is one of the first users who tried ToupTek Astro 2″ astrophotography filters. Let’s check out how he evaluates ToupTek Astro 2″ narrowband SHO filters in the review below.
The Importance of astronomical filters focus performance
When using a monochrome camera for deep-sky astrophotography, astronomical filter parameters, especially focus performance, are extremely crucial to getting high-quality nebula images. Different types of filters have varying impacts on imaging focus. Therefore, it is often required to refocus the telescope after switching filters when capturing multi-channel images. A significant deviation in focus from the previously used filters can cause issues, such as a defocused guide star in the OAG(Off-Axis Guider), which then requires re-focusing of the OAG.
For outdoor stargazers, this can quickly turn into a nightmare. Constantly switching filters and re-focusing the OAG throughout the night means little time for rest and can ruin an entire session. It is even worse for astrophotographers who conduct remote control in the observatory, as no one wants to be troublesome when only the observatory’s manager can help them refocus the OAG after switching filters.
How to measure astronomical filters focus performance
In an effort to minimize focus issues while using a monochrome camera, I invested in a set of filters from one of the highest-end domestic brands available. Using the “Filter Offset Calculator” plugin in N.I.N.Asoftware, I calculated the focus offset values for the seven filters I bought. The principle is that the plugin commands the entire setup to autofocus for each filter in three cycles, and then averages the focus step count to calculate the relative offset values between filters. The result showed that the maximum focus step difference between the LRGB and SHO filters was no more than 18 steps. This means the focus offsets are minimal, and switching between filters has little impact on the OAG guide star focus.
Focus offset calculation of domestic filters in N.I.N.A
Focus performance of ToupTek Astro 2″ astronomical filters
Unboxing and installing the ToupTek Astro 2″ filters to the filter wheel
When I received the full set of ToupTek Astro 2″ filters (2″ LRGB and SHO), I couldn’t get any information on the focus performance of ToupTek Astro filters from my friends. These filters were recently released and there were few users, even though ToupTek Astro filters were over 50% cheaper than the expensive brand I purchased before.
The filters were quite affordable, so I didn’t have high expectations for their focus performance. However, after performing the same focus offset calculation, I found that the maximum step difference between the ToupTek Astro LRGB and SHO filters was only 16 steps, which is almost the same as the domestic brand’s 18 steps. Regardless of which ToupTek Astro LRGB or SHO filter was used, the minimal focus offset value did not affect the guide star size in the OAG. This was quite surprising, especially given the price advantage of the ToupTek Astro filters.
Focus offset calculation of ToupTek Astro filters in N.I.N.A
Imaging results using ToupTek Astro 2″ astronomical filters
Outdoor Field Test
Thanks to the surprisingly strong focus performance of ToupTek Astro filters, I could rest easy while capturing a stunning 7-hour exposure of the NGC2237/Rosette Nebula . The slight star coma at the image edges was caused by the MPCC (Coma Corrector) being too long, which blocked part of the main mirror during focusing, not an issue with the filters or other equipment.
Imaging Equipment:
- Telescope: Sky-Watcher 150/750 + 0.85MPCC
- Telescope: BKP150/750 + 0.85MPCC
- Main Camera: ToupTek Astro ATR2600M
- Equatorial Mount: CLEARSKY ST17
- Filters: ToupTek Astro 2″ 6.5nm SHO
- Exposures: 47x300s (S), 19x300s (H), 22x300s (O)
- Total Exposure Time: 7.3 hours
2″H: 19x300s, only stretched
2″S: 47×300, only stretched
2″Oii : 22×300, only stretched
Kehuajin’s review highlights how ToupTek Astro 2″ narrowband SHO filters deliver exceptional focus performance—making them an excellent choice for deep-sky imaging enthusiasts.
To better satisfy astrophotographers’ needs, ToupTek has launched broadband and narrowband filters in 36mm, 1.25″, and 2″ sizes, with different bandpasses. The filters utilize advanced IAD (Ion-Assisted Deposition) coating technology, ensuring stability, high durability and minimal temperature drift, significantly extending the filter’s lifespan. More specifications and optical parameters introduction can be found in other articles. The filters feature anti-reflective coatings and high-transparency thin-film design, achieving over 90% transmittance while minimizing reflections and halo effects. Here is the summary of the optical parameters:
Astrophotographers can now save big with ToupTek Astro‘s DSO camera bundled deals, including the ATR585M and ATR533Mmonochrome cameras, filter sets, and filter wheels – all at an unbeatable price.
Click to Know More: https://www.touptekastro.com/collections/filters-filter-wheels
